vfio iommu type1: Add support for mediated devices

[mirror_ubuntu-eoan-kernel.git] / drivers / vfio / vfio_iommu_type1.c

/*
 * VFIO: IOMMU DMA mapping support for Type1 IOMMU
 *
 * Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
 *     Author: Alex Williamson <alex.williamson@redhat.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Derived from original vfio:
 * Copyright 2010 Cisco Systems, Inc.  All rights reserved.
 * Author: Tom Lyon, pugs@cisco.com
 *
 * We arbitrarily define a Type1 IOMMU as one matching the below code.
 * It could be called the x86 IOMMU as it's designed for AMD-Vi & Intel
 * VT-d, but that makes it harder to re-use as theoretically anyone
 * implementing a similar IOMMU could make use of this.  We expect the
 * IOMMU to support the IOMMU API and have few to no restrictions around
 * the IOVA range that can be mapped.  The Type1 IOMMU is currently
 * optimized for relatively static mappings of a userspace process with
 * userpsace pages pinned into memory.  We also assume devices and IOMMU
 * domains are PCI based as the IOMMU API is still centered around a
 * device/bus interface rather than a group interface.
 */

#include <linux/compat.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/iommu.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/rbtree.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/vfio.h>
#include <linux/workqueue.h>
#include <linux/pid_namespace.h>
#include <linux/mdev.h>

#define DRIVER_VERSION  "0.2"
#define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@redhat.com>"
#define DRIVER_DESC     "Type1 IOMMU driver for VFIO"

static bool allow_unsafe_interrupts;
module_param_named(allow_unsafe_interrupts,
                   allow_unsafe_interrupts, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(allow_unsafe_interrupts,
                 "Enable VFIO IOMMU support for on platforms without interrupt remapping support.");

static bool disable_hugepages;
module_param_named(disable_hugepages,
                   disable_hugepages, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(disable_hugepages,
                 "Disable VFIO IOMMU support for IOMMU hugepages.");

struct vfio_iommu {
        struct list_head        domain_list;
        struct vfio_domain      *external_domain; /* domain for external user */
        struct mutex            lock;
        struct rb_root          dma_list;
        bool                    v2;
        bool                    nesting;
};

struct vfio_domain {
        struct iommu_domain     *domain;
        struct list_head        next;
        struct list_head        group_list;
        int                     prot;           /* IOMMU_CACHE */
        bool                    fgsp;           /* Fine-grained super pages */
};

struct vfio_dma {
        struct rb_node          node;
        dma_addr_t              iova;           /* Device address */
        unsigned long           vaddr;          /* Process virtual addr */
        size_t                  size;           /* Map size (bytes) */
        int                     prot;           /* IOMMU_READ/WRITE */
        bool                    iommu_mapped;
        struct task_struct      *task;
        struct rb_root          pfn_list;       /* Ex-user pinned pfn list */
};

struct vfio_group {
        struct iommu_group      *iommu_group;
        struct list_head        next;
};

/*
 * Guest RAM pinning working set or DMA target
 */
struct vfio_pfn {
        struct rb_node          node;
        dma_addr_t              iova;           /* Device address */
        unsigned long           pfn;            /* Host pfn */
        atomic_t                ref_count;
};

#define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \
                                        (!list_empty(&iommu->domain_list))

static int put_pfn(unsigned long pfn, int prot);

/*
 * This code handles mapping and unmapping of user data buffers
 * into DMA'ble space using the IOMMU
 */

static struct vfio_dma *vfio_find_dma(struct vfio_iommu *iommu,
                                      dma_addr_t start, size_t size)
{
        struct rb_node *node = iommu->dma_list.rb_node;

        while (node) {
                struct vfio_dma *dma = rb_entry(node, struct vfio_dma, node);

                if (start + size <= dma->iova)
                        node = node->rb_left;
                else if (start >= dma->iova + dma->size)
                        node = node->rb_right;
                else
                        return dma;
        }

        return NULL;
}

static void vfio_link_dma(struct vfio_iommu *iommu, struct vfio_dma *new)
{
        struct rb_node **link = &iommu->dma_list.rb_node, *parent = NULL;
        struct vfio_dma *dma;

        while (*link) {
                parent = *link;
                dma = rb_entry(parent, struct vfio_dma, node);

                if (new->iova + new->size <= dma->iova)
                        link = &(*link)->rb_left;
                else
                        link = &(*link)->rb_right;
        }

        rb_link_node(&new->node, parent, link);
        rb_insert_color(&new->node, &iommu->dma_list);
}

static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
{
        rb_erase(&old->node, &iommu->dma_list);
}

/*
 * Helper Functions for host iova-pfn list
 */
static struct vfio_pfn *vfio_find_vpfn(struct vfio_dma *dma, dma_addr_t iova)
{
        struct vfio_pfn *vpfn;
        struct rb_node *node = dma->pfn_list.rb_node;

        while (node) {
                vpfn = rb_entry(node, struct vfio_pfn, node);

                if (iova < vpfn->iova)
                        node = node->rb_left;
                else if (iova > vpfn->iova)
                        node = node->rb_right;
                else
                        return vpfn;
        }
        return NULL;
}

static void vfio_link_pfn(struct vfio_dma *dma,
                          struct vfio_pfn *new)
{
        struct rb_node **link, *parent = NULL;
        struct vfio_pfn *vpfn;

        link = &dma->pfn_list.rb_node;
        while (*link) {
                parent = *link;
                vpfn = rb_entry(parent, struct vfio_pfn, node);

                if (new->iova < vpfn->iova)
                        link = &(*link)->rb_left;
                else
                        link = &(*link)->rb_right;
        }

        rb_link_node(&new->node, parent, link);
        rb_insert_color(&new->node, &dma->pfn_list);
}

static void vfio_unlink_pfn(struct vfio_dma *dma, struct vfio_pfn *old)
{
        rb_erase(&old->node, &dma->pfn_list);
}

static int vfio_add_to_pfn_list(struct vfio_dma *dma, dma_addr_t iova,
                                unsigned long pfn)
{
        struct vfio_pfn *vpfn;

        vpfn = kzalloc(sizeof(*vpfn), GFP_KERNEL);
        if (!vpfn)
                return -ENOMEM;

        vpfn->iova = iova;
        vpfn->pfn = pfn;
        atomic_set(&vpfn->ref_count, 1);
        vfio_link_pfn(dma, vpfn);
        return 0;
}

static void vfio_remove_from_pfn_list(struct vfio_dma *dma,
                                      struct vfio_pfn *vpfn)
{
        vfio_unlink_pfn(dma, vpfn);
        kfree(vpfn);
}

static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma,
                                               unsigned long iova)
{
        struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova);

        if (vpfn)
                atomic_inc(&vpfn->ref_count);
        return vpfn;
}

static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn)
{
        int ret = 0;

        if (atomic_dec_and_test(&vpfn->ref_count)) {
                ret = put_pfn(vpfn->pfn, dma->prot);
                vfio_remove_from_pfn_list(dma, vpfn);
        }
        return ret;
}

struct vwork {
        struct mm_struct        *mm;
        long                    npage;
        struct work_struct      work;
};

/* delayed decrement/increment for locked_vm */
static void vfio_lock_acct_bg(struct work_struct *work)
{
        struct vwork *vwork = container_of(work, struct vwork, work);
        struct mm_struct *mm;

        mm = vwork->mm;
        down_write(&mm->mmap_sem);
        mm->locked_vm += vwork->npage;
        up_write(&mm->mmap_sem);
        mmput(mm);
        kfree(vwork);
}

static void vfio_lock_acct(struct task_struct *task, long npage)
{
        struct vwork *vwork;
        struct mm_struct *mm;

        if (!npage)
                return;

        mm = get_task_mm(task);
        if (!mm)
                return; /* process exited or nothing to do */

        if (down_write_trylock(&mm->mmap_sem)) {
                mm->locked_vm += npage;
                up_write(&mm->mmap_sem);
                mmput(mm);
                return;
        }

        /*
         * Couldn't get mmap_sem lock, so must setup to update
         * mm->locked_vm later. If locked_vm were atomic, we
         * wouldn't need this silliness
         */
        vwork = kmalloc(sizeof(struct vwork), GFP_KERNEL);
        if (!vwork) {
                mmput(mm);
                return;
        }
        INIT_WORK(&vwork->work, vfio_lock_acct_bg);
        vwork->mm = mm;
        vwork->npage = npage;
        schedule_work(&vwork->work);
}

/*
 * Some mappings aren't backed by a struct page, for example an mmap'd
 * MMIO range for our own or another device.  These use a different
 * pfn conversion and shouldn't be tracked as locked pages.
 */
static bool is_invalid_reserved_pfn(unsigned long pfn)
{
        if (pfn_valid(pfn)) {
                bool reserved;
                struct page *tail = pfn_to_page(pfn);
                struct page *head = compound_head(tail);
                reserved = !!(PageReserved(head));
                if (head != tail) {
                        /*
                         * "head" is not a dangling pointer
                         * (compound_head takes care of that)
                         * but the hugepage may have been split
                         * from under us (and we may not hold a
                         * reference count on the head page so it can
                         * be reused before we run PageReferenced), so
                         * we've to check PageTail before returning
                         * what we just read.
                         */
                        smp_rmb();
                        if (PageTail(tail))
                                return reserved;
                }
                return PageReserved(tail);
        }

        return true;
}

static int put_pfn(unsigned long pfn, int prot)
{
        if (!is_invalid_reserved_pfn(pfn)) {
                struct page *page = pfn_to_page(pfn);
                if (prot & IOMMU_WRITE)
                        SetPageDirty(page);
                put_page(page);
                return 1;
        }
        return 0;
}

static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
                         int prot, unsigned long *pfn)
{
        struct page *page[1];
        struct vm_area_struct *vma;
        int ret;

        if (mm == current->mm) {
                ret = get_user_pages_fast(vaddr, 1, !!(prot & IOMMU_WRITE),
                                          page);
        } else {
                unsigned int flags = 0;

                if (prot & IOMMU_WRITE)
                        flags |= FOLL_WRITE;

                down_read(&mm->mmap_sem);
                ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page,
                                            NULL);
                up_read(&mm->mmap_sem);
        }

        if (ret == 1) {
                *pfn = page_to_pfn(page[0]);
                return 0;
        }

        down_read(&mm->mmap_sem);

        vma = find_vma_intersection(mm, vaddr, vaddr + 1);

        if (vma && vma->vm_flags & VM_PFNMAP) {
                *pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
                if (is_invalid_reserved_pfn(*pfn))
                        ret = 0;
        }

        up_read(&mm->mmap_sem);
        return ret;
}

/*
 * Attempt to pin pages.  We really don't want to track all the pfns and
 * the iommu can only map chunks of consecutive pfns anyway, so get the
 * first page and all consecutive pages with the same locking.
 */
static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
                                  long npage, unsigned long *pfn_base)
{
        unsigned long limit;
        bool lock_cap = ns_capable(task_active_pid_ns(dma->task)->user_ns,
                                   CAP_IPC_LOCK);
        struct mm_struct *mm;
        long ret, i = 0, lock_acct = 0;
        bool rsvd;
        dma_addr_t iova = vaddr - dma->vaddr + dma->iova;

        mm = get_task_mm(dma->task);
        if (!mm)
                return -ENODEV;

        ret = vaddr_get_pfn(mm, vaddr, dma->prot, pfn_base);
        if (ret)
                goto pin_pg_remote_exit;

        rsvd = is_invalid_reserved_pfn(*pfn_base);
        limit = task_rlimit(dma->task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;

        /*
         * Reserved pages aren't counted against the user, externally pinned
         * pages are already counted against the user.
         */
        if (!rsvd && !vfio_find_vpfn(dma, iova)) {
                if (!lock_cap && mm->locked_vm + 1 > limit) {
                        put_pfn(*pfn_base, dma->prot);
                        pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__,
                                        limit << PAGE_SHIFT);
                        ret = -ENOMEM;
                        goto pin_pg_remote_exit;
                }
                lock_acct++;
        }

        i++;
        if (likely(!disable_hugepages)) {
                /* Lock all the consecutive pages from pfn_base */
                for (vaddr += PAGE_SIZE, iova += PAGE_SIZE; i < npage;
                     i++, vaddr += PAGE_SIZE, iova += PAGE_SIZE) {
                        unsigned long pfn = 0;

                        ret = vaddr_get_pfn(mm, vaddr, dma->prot, &pfn);
                        if (ret)
                                break;

                        if (pfn != *pfn_base + i ||
                            rsvd != is_invalid_reserved_pfn(pfn)) {
                                put_pfn(pfn, dma->prot);
                                break;
                        }

                        if (!rsvd && !vfio_find_vpfn(dma, iova)) {
                                if (!lock_cap &&
                                    mm->locked_vm + lock_acct + 1 > limit) {
                                        put_pfn(pfn, dma->prot);
                                        pr_warn("%s: RLIMIT_MEMLOCK (%ld) "
                                                "exceeded\n", __func__,
                                                limit << PAGE_SHIFT);
                                        break;
                                }
                                lock_acct++;
                        }
                }
        }

        vfio_lock_acct(dma->task, lock_acct);
        ret = i;

pin_pg_remote_exit:
        mmput(mm);
        return ret;
}

static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
                                    unsigned long pfn, long npage,
                                    bool do_accounting)
{
        long unlocked = 0, locked = 0;
        long i;

        for (i = 0; i < npage; i++) {
                if (put_pfn(pfn++, dma->prot)) {
                        unlocked++;
                        if (vfio_find_vpfn(dma, iova + (i << PAGE_SHIFT)))
                                locked++;
                }
        }

        if (do_accounting)
                vfio_lock_acct(dma->task, locked - unlocked);

        return unlocked;
}

static int vfio_pin_page_external(struct vfio_dma *dma, unsigned long vaddr,
                                  unsigned long *pfn_base, bool do_accounting)
{
        unsigned long limit;
        bool lock_cap = ns_capable(task_active_pid_ns(dma->task)->user_ns,
                                   CAP_IPC_LOCK);
        struct mm_struct *mm;
        int ret;
        bool rsvd;

        mm = get_task_mm(dma->task);
        if (!mm)
                return -ENODEV;

        ret = vaddr_get_pfn(mm, vaddr, dma->prot, pfn_base);
        if (ret)
                goto pin_page_exit;

        rsvd = is_invalid_reserved_pfn(*pfn_base);
        limit = task_rlimit(dma->task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;

        if (!rsvd && !lock_cap && mm->locked_vm + 1 > limit) {
                put_pfn(*pfn_base, dma->prot);
                pr_warn("%s: Task %s (%d) RLIMIT_MEMLOCK (%ld) exceeded\n",
                        __func__, dma->task->comm, task_pid_nr(dma->task),
                        limit << PAGE_SHIFT);
                ret = -ENOMEM;
                goto pin_page_exit;
        }

        if (!rsvd && do_accounting)
                vfio_lock_acct(dma->task, 1);
        ret = 1;

pin_page_exit:
        mmput(mm);
        return ret;
}

static int vfio_unpin_page_external(struct vfio_dma *dma, dma_addr_t iova,
                                    bool do_accounting)
{
        int unlocked;
        struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova);

        if (!vpfn)
                return 0;

        unlocked = vfio_iova_put_vfio_pfn(dma, vpfn);

        if (do_accounting)
                vfio_lock_acct(dma->task, -unlocked);

        return unlocked;
}

static int vfio_iommu_type1_pin_pages(void *iommu_data,
                                      unsigned long *user_pfn,
                                      int npage, int prot,
                                      unsigned long *phys_pfn)
{
        struct vfio_iommu *iommu = iommu_data;
        int i, j, ret;
        unsigned long remote_vaddr;
        struct vfio_dma *dma;
        bool do_accounting;

        if (!iommu || !user_pfn || !phys_pfn)
                return -EINVAL;

        /* Supported for v2 version only */
        if (!iommu->v2)
                return -EACCES;

        mutex_lock(&iommu->lock);

        if (!iommu->external_domain) {
                ret = -EINVAL;
                goto pin_done;
        }

        /*
         * If iommu capable domain exist in the container then all pages are
         * already pinned and accounted. Accouting should be done if there is no
         * iommu capable domain in the container.
         */
        do_accounting = !IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu);

        for (i = 0; i < npage; i++) {
                dma_addr_t iova;
                struct vfio_pfn *vpfn;

                iova = user_pfn[i] << PAGE_SHIFT;
                dma = vfio_find_dma(iommu, iova, 0);
                if (!dma) {
                        ret = -EINVAL;
                        goto pin_unwind;
                }

                if ((dma->prot & prot) != prot) {
                        ret = -EPERM;
                        goto pin_unwind;
                }

                vpfn = vfio_iova_get_vfio_pfn(dma, iova);
                if (vpfn) {
                        phys_pfn[i] = vpfn->pfn;
                        continue;
                }

                remote_vaddr = dma->vaddr + iova - dma->iova;
                ret = vfio_pin_page_external(dma, remote_vaddr, &phys_pfn[i],
                                             do_accounting);
                if (ret <= 0) {
                        WARN_ON(!ret);
                        goto pin_unwind;
                }

                ret = vfio_add_to_pfn_list(dma, iova, phys_pfn[i]);
                if (ret) {
                        vfio_unpin_page_external(dma, iova, do_accounting);
                        goto pin_unwind;
                }
        }

        ret = i;
        goto pin_done;

pin_unwind:
        phys_pfn[i] = 0;
        for (j = 0; j < i; j++) {
                dma_addr_t iova;

                iova = user_pfn[j] << PAGE_SHIFT;
                dma = vfio_find_dma(iommu, iova, 0);
                vfio_unpin_page_external(dma, iova, do_accounting);
                phys_pfn[j] = 0;
        }
pin_done:
        mutex_unlock(&iommu->lock);
        return ret;
}

static int vfio_iommu_type1_unpin_pages(void *iommu_data,
                                        unsigned long *user_pfn,
                                        int npage)
{
        struct vfio_iommu *iommu = iommu_data;
        bool do_accounting;
        int i;

        if (!iommu || !user_pfn)
                return -EINVAL;

        /* Supported for v2 version only */
        if (!iommu->v2)
                return -EACCES;

        mutex_lock(&iommu->lock);

        if (!iommu->external_domain) {
                mutex_unlock(&iommu->lock);
                return -EINVAL;
        }

        do_accounting = !IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu);
        for (i = 0; i < npage; i++) {
                struct vfio_dma *dma;
                dma_addr_t iova;

                iova = user_pfn[i] << PAGE_SHIFT;
                dma = vfio_find_dma(iommu, iova, 0);
                if (!dma)
                        goto unpin_exit;
                vfio_unpin_page_external(dma, iova, do_accounting);
        }

unpin_exit:
        mutex_unlock(&iommu->lock);
        return i > npage ? npage : (i > 0 ? i : -EINVAL);
}

static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma,
                             bool do_accounting)
{
        dma_addr_t iova = dma->iova, end = dma->iova + dma->size;
        struct vfio_domain *domain, *d;
        long unlocked = 0;

        if (!dma->size)
                return 0;

        if (!IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu))
                return 0;

        /*
         * We use the IOMMU to track the physical addresses, otherwise we'd
         * need a much more complicated tracking system.  Unfortunately that
         * means we need to use one of the iommu domains to figure out the
         * pfns to unpin.  The rest need to be unmapped in advance so we have
         * no iommu translations remaining when the pages are unpinned.
         */
        domain = d = list_first_entry(&iommu->domain_list,
                                      struct vfio_domain, next);

        list_for_each_entry_continue(d, &iommu->domain_list, next) {
                iommu_unmap(d->domain, dma->iova, dma->size);
                cond_resched();
        }

        while (iova < end) {
                size_t unmapped, len;
                phys_addr_t phys, next;

                phys = iommu_iova_to_phys(domain->domain, iova);
                if (WARN_ON(!phys)) {
                        iova += PAGE_SIZE;
                        continue;
                }

                /*
                 * To optimize for fewer iommu_unmap() calls, each of which
                 * may require hardware cache flushing, try to find the
                 * largest contiguous physical memory chunk to unmap.
                 */
                for (len = PAGE_SIZE;
                     !domain->fgsp && iova + len < end; len += PAGE_SIZE) {
                        next = iommu_iova_to_phys(domain->domain, iova + len);
                        if (next != phys + len)
                                break;
                }

                unmapped = iommu_unmap(domain->domain, iova, len);
                if (WARN_ON(!unmapped))
                        break;

                unlocked += vfio_unpin_pages_remote(dma, iova,
                                                    phys >> PAGE_SHIFT,
                                                    unmapped >> PAGE_SHIFT,
                                                    false);
                iova += unmapped;

                cond_resched();
        }

        dma->iommu_mapped = false;
        if (do_accounting) {
                vfio_lock_acct(dma->task, -unlocked);
                return 0;
        }
        return unlocked;
}

static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
{
        vfio_unmap_unpin(iommu, dma, true);
        vfio_unlink_dma(iommu, dma);
        put_task_struct(dma->task);
        kfree(dma);
}

static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
{
        struct vfio_domain *domain;
        unsigned long bitmap = ULONG_MAX;

        mutex_lock(&iommu->lock);
        list_for_each_entry(domain, &iommu->domain_list, next)
                bitmap &= domain->domain->pgsize_bitmap;
        mutex_unlock(&iommu->lock);

        /*
         * In case the IOMMU supports page sizes smaller than PAGE_SIZE
         * we pretend PAGE_SIZE is supported and hide sub-PAGE_SIZE sizes.
         * That way the user will be able to map/unmap buffers whose size/
         * start address is aligned with PAGE_SIZE. Pinning code uses that
         * granularity while iommu driver can use the sub-PAGE_SIZE size
         * to map the buffer.
         */
        if (bitmap & ~PAGE_MASK) {
                bitmap &= PAGE_MASK;
                bitmap |= PAGE_SIZE;
        }

        return bitmap;
}

static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
                             struct vfio_iommu_type1_dma_unmap *unmap)
{
        uint64_t mask;
        struct vfio_dma *dma;
        size_t unmapped = 0;
        int ret = 0;

        mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;

        if (unmap->iova & mask)
                return -EINVAL;
        if (!unmap->size || unmap->size & mask)
                return -EINVAL;

        WARN_ON(mask & PAGE_MASK);

        mutex_lock(&iommu->lock);

        /*
         * vfio-iommu-type1 (v1) - User mappings were coalesced together to
         * avoid tracking individual mappings.  This means that the granularity
         * of the original mapping was lost and the user was allowed to attempt
         * to unmap any range.  Depending on the contiguousness of physical
         * memory and page sizes supported by the IOMMU, arbitrary unmaps may
         * or may not have worked.  We only guaranteed unmap granularity
         * matching the original mapping; even though it was untracked here,
         * the original mappings are reflected in IOMMU mappings.  This
         * resulted in a couple unusual behaviors.  First, if a range is not
         * able to be unmapped, ex. a set of 4k pages that was mapped as a
         * 2M hugepage into the IOMMU, the unmap ioctl returns success but with
         * a zero sized unmap.  Also, if an unmap request overlaps the first
         * address of a hugepage, the IOMMU will unmap the entire hugepage.
         * This also returns success and the returned unmap size reflects the
         * actual size unmapped.
         *
         * We attempt to maintain compatibility with this "v1" interface, but
         * we take control out of the hands of the IOMMU.  Therefore, an unmap
         * request offset from the beginning of the original mapping will
         * return success with zero sized unmap.  And an unmap request covering
         * the first iova of mapping will unmap the entire range.
         *
         * The v2 version of this interface intends to be more deterministic.
         * Unmap requests must fully cover previous mappings.  Multiple
         * mappings may still be unmaped by specifying large ranges, but there
         * must not be any previous mappings bisected by the range.  An error
         * will be returned if these conditions are not met.  The v2 interface
         * will only return success and a size of zero if there were no
         * mappings within the range.
         */
        if (iommu->v2) {
                dma = vfio_find_dma(iommu, unmap->iova, 0);
                if (dma && dma->iova != unmap->iova) {
                        ret = -EINVAL;
                        goto unlock;
                }
                dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0);
                if (dma && dma->iova + dma->size != unmap->iova + unmap->size) {
                        ret = -EINVAL;
                        goto unlock;
                }
        }

        while ((dma = vfio_find_dma(iommu, unmap->iova, unmap->size))) {
                if (!iommu->v2 && unmap->iova > dma->iova)
                        break;
                /*
                 * Task with same address space who mapped this iova range is
                 * allowed to unmap the iova range.
                 */
                if (dma->task->mm != current->mm)
                        break;
                unmapped += dma->size;
                vfio_remove_dma(iommu, dma);
        }

unlock:
        mutex_unlock(&iommu->lock);

        /* Report how much was unmapped */
        unmap->size = unmapped;

        return ret;
}

/*
 * Turns out AMD IOMMU has a page table bug where it won't map large pages
 * to a region that previously mapped smaller pages.  This should be fixed
 * soon, so this is just a temporary workaround to break mappings down into
 * PAGE_SIZE.  Better to map smaller pages than nothing.
 */
static int map_try_harder(struct vfio_domain *domain, dma_addr_t iova,
                          unsigned long pfn, long npage, int prot)
{
        long i;
        int ret = 0;

        for (i = 0; i < npage; i++, pfn++, iova += PAGE_SIZE) {
                ret = iommu_map(domain->domain, iova,
                                (phys_addr_t)pfn << PAGE_SHIFT,
                                PAGE_SIZE, prot | domain->prot);
                if (ret)
                        break;
        }

        for (; i < npage && i > 0; i--, iova -= PAGE_SIZE)
                iommu_unmap(domain->domain, iova, PAGE_SIZE);

        return ret;
}

static int vfio_iommu_map(struct vfio_iommu *iommu, dma_addr_t iova,
                          unsigned long pfn, long npage, int prot)
{
        struct vfio_domain *d;
        int ret;

        list_for_each_entry(d, &iommu->domain_list, next) {
                ret = iommu_map(d->domain, iova, (phys_addr_t)pfn << PAGE_SHIFT,
                                npage << PAGE_SHIFT, prot | d->prot);
                if (ret) {
                        if (ret != -EBUSY ||
                            map_try_harder(d, iova, pfn, npage, prot))
                                goto unwind;
                }

                cond_resched();
        }

        return 0;

unwind:
        list_for_each_entry_continue_reverse(d, &iommu->domain_list, next)
                iommu_unmap(d->domain, iova, npage << PAGE_SHIFT);

        return ret;
}

static int vfio_pin_map_dma(struct vfio_iommu *iommu, struct vfio_dma *dma,
                            size_t map_size)
{
        dma_addr_t iova = dma->iova;
        unsigned long vaddr = dma->vaddr;
        size_t size = map_size;
        long npage;
        unsigned long pfn;
        int ret = 0;

        while (size) {
                /* Pin a contiguous chunk of memory */
                npage = vfio_pin_pages_remote(dma, vaddr + dma->size,
                                              size >> PAGE_SHIFT, &pfn);
                if (npage <= 0) {
                        WARN_ON(!npage);
                        ret = (int)npage;
                        break;
                }

                /* Map it! */
                ret = vfio_iommu_map(iommu, iova + dma->size, pfn, npage,
                                     dma->prot);
                if (ret) {
                        vfio_unpin_pages_remote(dma, iova + dma->size, pfn,
                                                npage, true);
                        break;
                }

                size -= npage << PAGE_SHIFT;
                dma->size += npage << PAGE_SHIFT;
        }

        dma->iommu_mapped = true;

        if (ret)
                vfio_remove_dma(iommu, dma);

        return ret;
}

static int vfio_dma_do_map(struct vfio_iommu *iommu,
                           struct vfio_iommu_type1_dma_map *map)
{
        dma_addr_t iova = map->iova;
        unsigned long vaddr = map->vaddr;
        size_t size = map->size;
        int ret = 0, prot = 0;
        uint64_t mask;
        struct vfio_dma *dma;

        /* Verify that none of our __u64 fields overflow */
        if (map->size != size || map->vaddr != vaddr || map->iova != iova)
                return -EINVAL;

        mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;

        WARN_ON(mask & PAGE_MASK);

        /* READ/WRITE from device perspective */
        if (map->flags & VFIO_DMA_MAP_FLAG_WRITE)
                prot |= IOMMU_WRITE;
        if (map->flags & VFIO_DMA_MAP_FLAG_READ)
                prot |= IOMMU_READ;

        if (!prot || !size || (size | iova | vaddr) & mask)
                return -EINVAL;

        /* Don't allow IOVA or virtual address wrap */
        if (iova + size - 1 < iova || vaddr + size - 1 < vaddr)
                return -EINVAL;

        mutex_lock(&iommu->lock);

        if (vfio_find_dma(iommu, iova, size)) {
                ret = -EEXIST;
                goto out_unlock;
        }

        dma = kzalloc(sizeof(*dma), GFP_KERNEL);
        if (!dma) {
                ret = -ENOMEM;
                goto out_unlock;
        }

        dma->iova = iova;
        dma->vaddr = vaddr;
        dma->prot = prot;
        get_task_struct(current);
        dma->task = current;
        dma->pfn_list = RB_ROOT;

        /* Insert zero-sized and grow as we map chunks of it */
        vfio_link_dma(iommu, dma);

        /* Don't pin and map if container doesn't contain IOMMU capable domain*/
        if (!IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu))
                dma->size = size;
        else
                ret = vfio_pin_map_dma(iommu, dma, size);

out_unlock:
        mutex_unlock(&iommu->lock);
        return ret;
}

static int vfio_bus_type(struct device *dev, void *data)
{
        struct bus_type **bus = data;

        if (*bus && *bus != dev->bus)
                return -EINVAL;

        *bus = dev->bus;

        return 0;
}

static int vfio_iommu_replay(struct vfio_iommu *iommu,
                             struct vfio_domain *domain)
{
        struct vfio_domain *d;
        struct rb_node *n;
        int ret;

        /* Arbitrarily pick the first domain in the list for lookups */
        d = list_first_entry(&iommu->domain_list, struct vfio_domain, next);
        n = rb_first(&iommu->dma_list);

        for (; n; n = rb_next(n)) {
                struct vfio_dma *dma;
                dma_addr_t iova;

                dma = rb_entry(n, struct vfio_dma, node);
                iova = dma->iova;

                while (iova < dma->iova + dma->size) {
                        phys_addr_t phys;
                        size_t size;

                        if (dma->iommu_mapped) {
                                phys_addr_t p;
                                dma_addr_t i;

                                phys = iommu_iova_to_phys(d->domain, iova);

                                if (WARN_ON(!phys)) {
                                        iova += PAGE_SIZE;
                                        continue;
                                }

                                size = PAGE_SIZE;
                                p = phys + size;
                                i = iova + size;
                                while (i < dma->iova + dma->size &&
                                       p == iommu_iova_to_phys(d->domain, i)) {
                                        size += PAGE_SIZE;
                                        p += PAGE_SIZE;
                                        i += PAGE_SIZE;
                                }
                        } else {
                                unsigned long pfn;
                                unsigned long vaddr = dma->vaddr +
                                                     (iova - dma->iova);
                                size_t n = dma->iova + dma->size - iova;
                                long npage;

                                npage = vfio_pin_pages_remote(dma, vaddr,
                                                              n >> PAGE_SHIFT,
                                                              &pfn);
                                if (npage <= 0) {
                                        WARN_ON(!npage);
                                        ret = (int)npage;
                                        return ret;
                                }

                                phys = pfn << PAGE_SHIFT;
                                size = npage << PAGE_SHIFT;
                        }

                        ret = iommu_map(domain->domain, iova, phys,
                                        size, dma->prot | domain->prot);
                        if (ret)
                                return ret;

                        iova += size;
                }
                dma->iommu_mapped = true;
        }
        return 0;
}

/*
 * We change our unmap behavior slightly depending on whether the IOMMU
 * supports fine-grained superpages.  IOMMUs like AMD-Vi will use a superpage
 * for practically any contiguous power-of-two mapping we give it.  This means
 * we don't need to look for contiguous chunks ourselves to make unmapping
 * more efficient.  On IOMMUs with coarse-grained super pages, like Intel VT-d
 * with discrete 2M/1G/512G/1T superpages, identifying contiguous chunks
 * significantly boosts non-hugetlbfs mappings and doesn't seem to hurt when
 * hugetlbfs is in use.
 */
static void vfio_test_domain_fgsp(struct vfio_domain *domain)
{
        struct page *pages;
        int ret, order = get_order(PAGE_SIZE * 2);

        pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, order);
        if (!pages)
                return;

        ret = iommu_map(domain->domain, 0, page_to_phys(pages), PAGE_SIZE * 2,
                        IOMMU_READ | IOMMU_WRITE | domain->prot);
        if (!ret) {
                size_t unmapped = iommu_unmap(domain->domain, 0, PAGE_SIZE);

                if (unmapped == PAGE_SIZE)
                        iommu_unmap(domain->domain, PAGE_SIZE, PAGE_SIZE);
                else
                        domain->fgsp = true;
        }

        __free_pages(pages, order);
}

static struct vfio_group *find_iommu_group(struct vfio_domain *domain,
                                           struct iommu_group *iommu_group)
{
        struct vfio_group *g;

        list_for_each_entry(g, &domain->group_list, next) {
                if (g->iommu_group == iommu_group)
                        return g;
        }

        return NULL;
}

static int vfio_iommu_type1_attach_group(void *iommu_data,
                                         struct iommu_group *iommu_group)
{
        struct vfio_iommu *iommu = iommu_data;
        struct vfio_group *group;
        struct vfio_domain *domain, *d;
        struct bus_type *bus = NULL, *mdev_bus;
        int ret;

        mutex_lock(&iommu->lock);

        list_for_each_entry(d, &iommu->domain_list, next) {
                if (find_iommu_group(d, iommu_group)) {
                        mutex_unlock(&iommu->lock);
                        return -EINVAL;
                }
        }

        if (iommu->external_domain) {
                if (find_iommu_group(iommu->external_domain, iommu_group)) {
                        mutex_unlock(&iommu->lock);
                        return -EINVAL;
                }
        }

        group = kzalloc(sizeof(*group), GFP_KERNEL);
        domain = kzalloc(sizeof(*domain), GFP_KERNEL);
        if (!group || !domain) {
                ret = -ENOMEM;
                goto out_free;
        }

        group->iommu_group = iommu_group;

        /* Determine bus_type in order to allocate a domain */
        ret = iommu_group_for_each_dev(iommu_group, &bus, vfio_bus_type);
        if (ret)
                goto out_free;

        mdev_bus = symbol_get(mdev_bus_type);

        if (mdev_bus) {
                if ((bus == mdev_bus) && !iommu_present(bus)) {
                        symbol_put(mdev_bus_type);
                        if (!iommu->external_domain) {
                                INIT_LIST_HEAD(&domain->group_list);
                                iommu->external_domain = domain;
                        } else
                                kfree(domain);

                        list_add(&group->next,
                                 &iommu->external_domain->group_list);
                        mutex_unlock(&iommu->lock);
                        return 0;
                }
                symbol_put(mdev_bus_type);
        }

        domain->domain = iommu_domain_alloc(bus);
        if (!domain->domain) {
                ret = -EIO;
                goto out_free;
        }

        if (iommu->nesting) {
                int attr = 1;

                ret = iommu_domain_set_attr(domain->domain, DOMAIN_ATTR_NESTING,
                                            &attr);
                if (ret)
                        goto out_domain;
        }

        ret = iommu_attach_group(domain->domain, iommu_group);
        if (ret)
                goto out_domain;

        INIT_LIST_HEAD(&domain->group_list);
        list_add(&group->next, &domain->group_list);

        if (!allow_unsafe_interrupts &&
            !iommu_capable(bus, IOMMU_CAP_INTR_REMAP)) {
                pr_warn("%s: No interrupt remapping support.  Use the module param \"allow_unsafe_interrupts\" to enable VFIO IOMMU support on this platform\n",
                       __func__);
                ret = -EPERM;
                goto out_detach;
        }

        if (iommu_capable(bus, IOMMU_CAP_CACHE_COHERENCY))
                domain->prot |= IOMMU_CACHE;

        /*
         * Try to match an existing compatible domain.  We don't want to
         * preclude an IOMMU driver supporting multiple bus_types and being
         * able to include different bus_types in the same IOMMU domain, so
         * we test whether the domains use the same iommu_ops rather than
         * testing if they're on the same bus_type.
         */
        list_for_each_entry(d, &iommu->domain_list, next) {
                if (d->domain->ops == domain->domain->ops &&
                    d->prot == domain->prot) {
                        iommu_detach_group(domain->domain, iommu_group);
                        if (!iommu_attach_group(d->domain, iommu_group)) {
                                list_add(&group->next, &d->group_list);
                                iommu_domain_free(domain->domain);
                                kfree(domain);
                                mutex_unlock(&iommu->lock);
                                return 0;
                        }

                        ret = iommu_attach_group(domain->domain, iommu_group);
                        if (ret)
                                goto out_domain;
                }
        }

        vfio_test_domain_fgsp(domain);

        /* replay mappings on new domains */
        ret = vfio_iommu_replay(iommu, domain);
        if (ret)
                goto out_detach;

        list_add(&domain->next, &iommu->domain_list);

        mutex_unlock(&iommu->lock);

        return 0;

out_detach:
        iommu_detach_group(domain->domain, iommu_group);
out_domain:
        iommu_domain_free(domain->domain);
out_free:
        kfree(domain);
        kfree(group);
        mutex_unlock(&iommu->lock);
        return ret;
}

static void vfio_iommu_unmap_unpin_all(struct vfio_iommu *iommu)
{
        struct rb_node *node;

        while ((node = rb_first(&iommu->dma_list)))
                vfio_remove_dma(iommu, rb_entry(node, struct vfio_dma, node));
}

static void vfio_iommu_unmap_unpin_reaccount(struct vfio_iommu *iommu)
{
        struct rb_node *n, *p;

        n = rb_first(&iommu->dma_list);
        for (; n; n = rb_next(n)) {
                struct vfio_dma *dma;
                long locked = 0, unlocked = 0;

                dma = rb_entry(n, struct vfio_dma, node);
                unlocked += vfio_unmap_unpin(iommu, dma, false);
                p = rb_first(&dma->pfn_list);
                for (; p; p = rb_next(p)) {
                        struct vfio_pfn *vpfn = rb_entry(p, struct vfio_pfn,
                                                         node);

                        if (!is_invalid_reserved_pfn(vpfn->pfn))
                                locked++;
                }
                vfio_lock_acct(dma->task, locked - unlocked);
        }
}

static void vfio_sanity_check_pfn_list(struct vfio_iommu *iommu)
{
        struct rb_node *n;

        n = rb_first(&iommu->dma_list);
        for (; n; n = rb_next(n)) {
                struct vfio_dma *dma;

                dma = rb_entry(n, struct vfio_dma, node);

                if (WARN_ON(!RB_EMPTY_ROOT(&dma->pfn_list)))
                        break;
        }
}

static void vfio_iommu_type1_detach_group(void *iommu_data,
                                          struct iommu_group *iommu_group)
{
        struct vfio_iommu *iommu = iommu_data;
        struct vfio_domain *domain;
        struct vfio_group *group;

        mutex_lock(&iommu->lock);

        if (iommu->external_domain) {
                group = find_iommu_group(iommu->external_domain, iommu_group);
                if (group) {
                        list_del(&group->next);
                        kfree(group);

                        if (list_empty(&iommu->external_domain->group_list)) {
                                vfio_sanity_check_pfn_list(iommu);

                                if (!IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu))
                                        vfio_iommu_unmap_unpin_all(iommu);

                                kfree(iommu->external_domain);
                                iommu->external_domain = NULL;
                        }
                        goto detach_group_done;
                }
        }

        list_for_each_entry(domain, &iommu->domain_list, next) {
                group = find_iommu_group(domain, iommu_group);
                if (!group)
                        continue;

                iommu_detach_group(domain->domain, iommu_group);
                list_del(&group->next);
                kfree(group);
                /*
                 * Group ownership provides privilege, if the group list is
                 * empty, the domain goes away. If it's the last domain with
                 * iommu and external domain doesn't exist, then all the
                 * mappings go away too. If it's the last domain with iommu and
                 * external domain exist, update accounting
                 */
                if (list_empty(&domain->group_list)) {
                        if (list_is_singular(&iommu->domain_list)) {
                                if (!iommu->external_domain)
                                        vfio_iommu_unmap_unpin_all(iommu);
                                else
                                        vfio_iommu_unmap_unpin_reaccount(iommu);
                        }
                        iommu_domain_free(domain->domain);
                        list_del(&domain->next);
                        kfree(domain);
                }
                break;
        }

detach_group_done:
        mutex_unlock(&iommu->lock);
}

static void *vfio_iommu_type1_open(unsigned long arg)
{
        struct vfio_iommu *iommu;

        iommu = kzalloc(sizeof(*iommu), GFP_KERNEL);
        if (!iommu)
                return ERR_PTR(-ENOMEM);

        switch (arg) {
        case VFIO_TYPE1_IOMMU:
                break;
        case VFIO_TYPE1_NESTING_IOMMU:
                iommu->nesting = true;
        case VFIO_TYPE1v2_IOMMU:
                iommu->v2 = true;
                break;
        default:
                kfree(iommu);
                return ERR_PTR(-EINVAL);
        }

        INIT_LIST_HEAD(&iommu->domain_list);
        iommu->dma_list = RB_ROOT;
        mutex_init(&iommu->lock);

        return iommu;
}

static void vfio_release_domain(struct vfio_domain *domain, bool external)
{
        struct vfio_group *group, *group_tmp;

        list_for_each_entry_safe(group, group_tmp,
                                 &domain->group_list, next) {
                if (!external)
                        iommu_detach_group(domain->domain, group->iommu_group);
                list_del(&group->next);
                kfree(group);
        }

        if (!external)
                iommu_domain_free(domain->domain);
}

static void vfio_iommu_type1_release(void *iommu_data)
{
        struct vfio_iommu *iommu = iommu_data;
        struct vfio_domain *domain, *domain_tmp;

        if (iommu->external_domain) {
                vfio_release_domain(iommu->external_domain, true);
                vfio_sanity_check_pfn_list(iommu);
                kfree(iommu->external_domain);
        }

        vfio_iommu_unmap_unpin_all(iommu);

        list_for_each_entry_safe(domain, domain_tmp,
                                 &iommu->domain_list, next) {
                vfio_release_domain(domain, false);
                list_del(&domain->next);
                kfree(domain);
        }
        kfree(iommu);
}

static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
{
        struct vfio_domain *domain;
        int ret = 1;

        mutex_lock(&iommu->lock);
        list_for_each_entry(domain, &iommu->domain_list, next) {
                if (!(domain->prot & IOMMU_CACHE)) {
                        ret = 0;
                        break;
                }
        }
        mutex_unlock(&iommu->lock);

        return ret;
}

static long vfio_iommu_type1_ioctl(void *iommu_data,
                                   unsigned int cmd, unsigned long arg)
{
        struct vfio_iommu *iommu = iommu_data;
        unsigned long minsz;

        if (cmd == VFIO_CHECK_EXTENSION) {
                switch (arg) {
                case VFIO_TYPE1_IOMMU:
                case VFIO_TYPE1v2_IOMMU:
                case VFIO_TYPE1_NESTING_IOMMU:
                        return 1;
                case VFIO_DMA_CC_IOMMU:
                        if (!iommu)
                                return 0;
                        return vfio_domains_have_iommu_cache(iommu);
                default:
                        return 0;
                }
        } else if (cmd == VFIO_IOMMU_GET_INFO) {
                struct vfio_iommu_type1_info info;

                minsz = offsetofend(struct vfio_iommu_type1_info, iova_pgsizes);

                if (copy_from_user(&info, (void __user *)arg, minsz))
                        return -EFAULT;

                if (info.argsz < minsz)
                        return -EINVAL;

                info.flags = VFIO_IOMMU_INFO_PGSIZES;

                info.iova_pgsizes = vfio_pgsize_bitmap(iommu);

                return copy_to_user((void __user *)arg, &info, minsz) ?
                        -EFAULT : 0;

        } else if (cmd == VFIO_IOMMU_MAP_DMA) {
                struct vfio_iommu_type1_dma_map map;
                uint32_t mask = VFIO_DMA_MAP_FLAG_READ |
                                VFIO_DMA_MAP_FLAG_WRITE;

                minsz = offsetofend(struct vfio_iommu_type1_dma_map, size);

                if (copy_from_user(&map, (void __user *)arg, minsz))
                        return -EFAULT;

                if (map.argsz < minsz || map.flags & ~mask)
                        return -EINVAL;

                return vfio_dma_do_map(iommu, &map);

        } else if (cmd == VFIO_IOMMU_UNMAP_DMA) {
                struct vfio_iommu_type1_dma_unmap unmap;
                long ret;

                minsz = offsetofend(struct vfio_iommu_type1_dma_unmap, size);

                if (copy_from_user(&unmap, (void __user *)arg, minsz))
                        return -EFAULT;

                if (unmap.argsz < minsz || unmap.flags)
                        return -EINVAL;

                ret = vfio_dma_do_unmap(iommu, &unmap);
                if (ret)
                        return ret;

                return copy_to_user((void __user *)arg, &unmap, minsz) ?
                        -EFAULT : 0;
        }

        return -ENOTTY;
}

static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
        .name           = "vfio-iommu-type1",
        .owner          = THIS_MODULE,
        .open           = vfio_iommu_type1_open,
        .release        = vfio_iommu_type1_release,
        .ioctl          = vfio_iommu_type1_ioctl,
        .attach_group   = vfio_iommu_type1_attach_group,
        .detach_group   = vfio_iommu_type1_detach_group,
        .pin_pages      = vfio_iommu_type1_pin_pages,
        .unpin_pages    = vfio_iommu_type1_unpin_pages,
};

static int __init vfio_iommu_type1_init(void)
{
        return vfio_register_iommu_driver(&vfio_iommu_driver_ops_type1);
}

static void __exit vfio_iommu_type1_cleanup(void)
{
        vfio_unregister_iommu_driver(&vfio_iommu_driver_ops_type1);
}

module_init(vfio_iommu_type1_init);
module_exit(vfio_iommu_type1_cleanup);

MODULE_VERSION(DRIVER_VERSION);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);