Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

[mirror_ubuntu-kernels.git] / arch / s390 / kernel / uv.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Common Ultravisor functions and initialization
 *
 * Copyright IBM Corp. 2019, 2020
 */
#define KMSG_COMPONENT "prot_virt"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/sizes.h>
#include <linux/bitmap.h>
#include <linux/memblock.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <asm/facility.h>
#include <asm/sections.h>
#include <asm/uv.h>

/* the bootdata_preserved fields come from ones in arch/s390/boot/uv.c */
#ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
int __bootdata_preserved(prot_virt_guest);
#endif

/*
 * uv_info contains both host and guest information but it's currently only
 * expected to be used within modules if it's the KVM module or for
 * any PV guest module.
 *
 * The kernel itself will write these values once in uv_query_info()
 * and then make some of them readable via a sysfs interface.
 */
struct uv_info __bootdata_preserved(uv_info);
EXPORT_SYMBOL(uv_info);

#if IS_ENABLED(CONFIG_KVM)
int __bootdata_preserved(prot_virt_host);
EXPORT_SYMBOL(prot_virt_host);

static int __init uv_init(phys_addr_t stor_base, unsigned long stor_len)
{
        struct uv_cb_init uvcb = {
                .header.cmd = UVC_CMD_INIT_UV,
                .header.len = sizeof(uvcb),
                .stor_origin = stor_base,
                .stor_len = stor_len,
        };

        if (uv_call(0, (uint64_t)&uvcb)) {
                pr_err("Ultravisor init failed with rc: 0x%x rrc: 0%x\n",
                       uvcb.header.rc, uvcb.header.rrc);
                return -1;
        }
        return 0;
}

void __init setup_uv(void)
{
        void *uv_stor_base;

        if (!is_prot_virt_host())
                return;

        uv_stor_base = memblock_alloc_try_nid(
                uv_info.uv_base_stor_len, SZ_1M, SZ_2G,
                MEMBLOCK_ALLOC_ACCESSIBLE, NUMA_NO_NODE);
        if (!uv_stor_base) {
                pr_warn("Failed to reserve %lu bytes for ultravisor base storage\n",
                        uv_info.uv_base_stor_len);
                goto fail;
        }

        if (uv_init(__pa(uv_stor_base), uv_info.uv_base_stor_len)) {
                memblock_free(uv_stor_base, uv_info.uv_base_stor_len);
                goto fail;
        }

        pr_info("Reserving %luMB as ultravisor base storage\n",
                uv_info.uv_base_stor_len >> 20);
        return;
fail:
        pr_info("Disabling support for protected virtualization");
        prot_virt_host = 0;
}

/*
 * Requests the Ultravisor to pin the page in the shared state. This will
 * cause an intercept when the guest attempts to unshare the pinned page.
 */
static int uv_pin_shared(unsigned long paddr)
{
        struct uv_cb_cfs uvcb = {
                .header.cmd = UVC_CMD_PIN_PAGE_SHARED,
                .header.len = sizeof(uvcb),
                .paddr = paddr,
        };

        if (uv_call(0, (u64)&uvcb))
                return -EINVAL;
        return 0;
}

/*
 * Requests the Ultravisor to destroy a guest page and make it
 * accessible to the host. The destroy clears the page instead of
 * exporting.
 *
 * @paddr: Absolute host address of page to be destroyed
 */
static int uv_destroy_page(unsigned long paddr)
{
        struct uv_cb_cfs uvcb = {
                .header.cmd = UVC_CMD_DESTR_SEC_STOR,
                .header.len = sizeof(uvcb),
                .paddr = paddr
        };

        if (uv_call(0, (u64)&uvcb)) {
                /*
                 * Older firmware uses 107/d as an indication of a non secure
                 * page. Let us emulate the newer variant (no-op).
                 */
                if (uvcb.header.rc == 0x107 && uvcb.header.rrc == 0xd)
                        return 0;
                return -EINVAL;
        }
        return 0;
}

/*
 * The caller must already hold a reference to the page
 */
int uv_destroy_owned_page(unsigned long paddr)
{
        struct page *page = phys_to_page(paddr);
        int rc;

        get_page(page);
        rc = uv_destroy_page(paddr);
        if (!rc)
                clear_bit(PG_arch_1, &page->flags);
        put_page(page);
        return rc;
}

/*
 * Requests the Ultravisor to encrypt a guest page and make it
 * accessible to the host for paging (export).
 *
 * @paddr: Absolute host address of page to be exported
 */
int uv_convert_from_secure(unsigned long paddr)
{
        struct uv_cb_cfs uvcb = {
                .header.cmd = UVC_CMD_CONV_FROM_SEC_STOR,
                .header.len = sizeof(uvcb),
                .paddr = paddr
        };

        if (uv_call(0, (u64)&uvcb))
                return -EINVAL;
        return 0;
}

/*
 * The caller must already hold a reference to the page
 */
int uv_convert_owned_from_secure(unsigned long paddr)
{
        struct page *page = phys_to_page(paddr);
        int rc;

        get_page(page);
        rc = uv_convert_from_secure(paddr);
        if (!rc)
                clear_bit(PG_arch_1, &page->flags);
        put_page(page);
        return rc;
}

/*
 * Calculate the expected ref_count for a page that would otherwise have no
 * further pins. This was cribbed from similar functions in other places in
 * the kernel, but with some slight modifications. We know that a secure
 * page can not be a huge page for example.
 */
static int expected_page_refs(struct page *page)
{
        int res;

        res = page_mapcount(page);
        if (PageSwapCache(page)) {
                res++;
        } else if (page_mapping(page)) {
                res++;
                if (page_has_private(page))
                        res++;
        }
        return res;
}

static int make_page_secure(struct page *page, struct uv_cb_header *uvcb)
{
        int expected, cc = 0;

        if (PageWriteback(page))
                return -EAGAIN;
        expected = expected_page_refs(page);
        if (!page_ref_freeze(page, expected))
                return -EBUSY;
        set_bit(PG_arch_1, &page->flags);
        /*
         * If the UVC does not succeed or fail immediately, we don't want to
         * loop for long, or we might get stall notifications.
         * On the other hand, this is a complex scenario and we are holding a lot of
         * locks, so we can't easily sleep and reschedule. We try only once,
         * and if the UVC returned busy or partial completion, we return
         * -EAGAIN and we let the callers deal with it.
         */
        cc = __uv_call(0, (u64)uvcb);
        page_ref_unfreeze(page, expected);
        /*
         * Return -ENXIO if the page was not mapped, -EINVAL for other errors.
         * If busy or partially completed, return -EAGAIN.
         */
        if (cc == UVC_CC_OK)
                return 0;
        else if (cc == UVC_CC_BUSY || cc == UVC_CC_PARTIAL)
                return -EAGAIN;
        return uvcb->rc == 0x10a ? -ENXIO : -EINVAL;
}

/**
 * should_export_before_import - Determine whether an export is needed
 * before an import-like operation
 * @uvcb: the Ultravisor control block of the UVC to be performed
 * @mm: the mm of the process
 *
 * Returns whether an export is needed before every import-like operation.
 * This is needed for shared pages, which don't trigger a secure storage
 * exception when accessed from a different guest.
 *
 * Although considered as one, the Unpin Page UVC is not an actual import,
 * so it is not affected.
 *
 * No export is needed also when there is only one protected VM, because the
 * page cannot belong to the wrong VM in that case (there is no "other VM"
 * it can belong to).
 *
 * Return: true if an export is needed before every import, otherwise false.
 */
static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
{
        /*
         * The misc feature indicates, among other things, that importing a
         * shared page from a different protected VM will automatically also
         * transfer its ownership.
         */
        if (test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications))
                return false;
        if (uvcb->cmd == UVC_CMD_UNPIN_PAGE_SHARED)
                return false;
        return atomic_read(&mm->context.protected_count) > 1;
}

/*
 * Requests the Ultravisor to make a page accessible to a guest.
 * If it's brought in the first time, it will be cleared. If
 * it has been exported before, it will be decrypted and integrity
 * checked.
 */
int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)
{
        struct vm_area_struct *vma;
        bool local_drain = false;
        spinlock_t *ptelock;
        unsigned long uaddr;
        struct page *page;
        pte_t *ptep;
        int rc;

again:
        rc = -EFAULT;
        mmap_read_lock(gmap->mm);

        uaddr = __gmap_translate(gmap, gaddr);
        if (IS_ERR_VALUE(uaddr))
                goto out;
        vma = vma_lookup(gmap->mm, uaddr);
        if (!vma)
                goto out;
        /*
         * Secure pages cannot be huge and userspace should not combine both.
         * In case userspace does it anyway this will result in an -EFAULT for
         * the unpack. The guest is thus never reaching secure mode. If
         * userspace is playing dirty tricky with mapping huge pages later
         * on this will result in a segmentation fault.
         */
        if (is_vm_hugetlb_page(vma))
                goto out;

        rc = -ENXIO;
        ptep = get_locked_pte(gmap->mm, uaddr, &ptelock);
        if (!ptep)
                goto out;
        if (pte_present(*ptep) && !(pte_val(*ptep) & _PAGE_INVALID) && pte_write(*ptep)) {
                page = pte_page(*ptep);
                rc = -EAGAIN;
                if (trylock_page(page)) {
                        if (should_export_before_import(uvcb, gmap->mm))
                                uv_convert_from_secure(page_to_phys(page));
                        rc = make_page_secure(page, uvcb);
                        unlock_page(page);
                }
        }
        pte_unmap_unlock(ptep, ptelock);
out:
        mmap_read_unlock(gmap->mm);

        if (rc == -EAGAIN) {
                /*
                 * If we are here because the UVC returned busy or partial
                 * completion, this is just a useless check, but it is safe.
                 */
                wait_on_page_writeback(page);
        } else if (rc == -EBUSY) {
                /*
                 * If we have tried a local drain and the page refcount
                 * still does not match our expected safe value, try with a
                 * system wide drain. This is needed if the pagevecs holding
                 * the page are on a different CPU.
                 */
                if (local_drain) {
                        lru_add_drain_all();
                        /* We give up here, and let the caller try again */
                        return -EAGAIN;
                }
                /*
                 * We are here if the page refcount does not match the
                 * expected safe value. The main culprits are usually
                 * pagevecs. With lru_add_drain() we drain the pagevecs
                 * on the local CPU so that hopefully the refcount will
                 * reach the expected safe value.
                 */
                lru_add_drain();
                local_drain = true;
                /* And now we try again immediately after draining */
                goto again;
        } else if (rc == -ENXIO) {
                if (gmap_fault(gmap, gaddr, FAULT_FLAG_WRITE))
                        return -EFAULT;
                return -EAGAIN;
        }
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_make_secure);

int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr)
{
        struct uv_cb_cts uvcb = {
                .header.cmd = UVC_CMD_CONV_TO_SEC_STOR,
                .header.len = sizeof(uvcb),
                .guest_handle = gmap->guest_handle,
                .gaddr = gaddr,
        };

        return gmap_make_secure(gmap, gaddr, &uvcb);
}
EXPORT_SYMBOL_GPL(gmap_convert_to_secure);

/**
 * gmap_destroy_page - Destroy a guest page.
 * @gmap: the gmap of the guest
 * @gaddr: the guest address to destroy
 *
 * An attempt will be made to destroy the given guest page. If the attempt
 * fails, an attempt is made to export the page. If both attempts fail, an
 * appropriate error is returned.
 */
int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
{
        struct vm_area_struct *vma;
        unsigned long uaddr;
        struct page *page;
        int rc;

        rc = -EFAULT;
        mmap_read_lock(gmap->mm);

        uaddr = __gmap_translate(gmap, gaddr);
        if (IS_ERR_VALUE(uaddr))
                goto out;
        vma = vma_lookup(gmap->mm, uaddr);
        if (!vma)
                goto out;
        /*
         * Huge pages should not be able to become secure
         */
        if (is_vm_hugetlb_page(vma))
                goto out;

        rc = 0;
        /* we take an extra reference here */
        page = follow_page(vma, uaddr, FOLL_WRITE | FOLL_GET);
        if (IS_ERR_OR_NULL(page))
                goto out;
        rc = uv_destroy_owned_page(page_to_phys(page));
        /*
         * Fault handlers can race; it is possible that two CPUs will fault
         * on the same secure page. One CPU can destroy the page, reboot,
         * re-enter secure mode and import it, while the second CPU was
         * stuck at the beginning of the handler. At some point the second
         * CPU will be able to progress, and it will not be able to destroy
         * the page. In that case we do not want to terminate the process,
         * we instead try to export the page.
         */
        if (rc)
                rc = uv_convert_owned_from_secure(page_to_phys(page));
        put_page(page);
out:
        mmap_read_unlock(gmap->mm);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_destroy_page);

/*
 * To be called with the page locked or with an extra reference! This will
 * prevent gmap_make_secure from touching the page concurrently. Having 2
 * parallel make_page_accessible is fine, as the UV calls will become a
 * no-op if the page is already exported.
 */
int arch_make_page_accessible(struct page *page)
{
        int rc = 0;

        /* Hugepage cannot be protected, so nothing to do */
        if (PageHuge(page))
                return 0;

        /*
         * PG_arch_1 is used in 3 places:
         * 1. for kernel page tables during early boot
         * 2. for storage keys of huge pages and KVM
         * 3. As an indication that this page might be secure. This can
         *    overindicate, e.g. we set the bit before calling
         *    convert_to_secure.
         * As secure pages are never huge, all 3 variants can co-exists.
         */
        if (!test_bit(PG_arch_1, &page->flags))
                return 0;

        rc = uv_pin_shared(page_to_phys(page));
        if (!rc) {
                clear_bit(PG_arch_1, &page->flags);
                return 0;
        }

        rc = uv_convert_from_secure(page_to_phys(page));
        if (!rc) {
                clear_bit(PG_arch_1, &page->flags);
                return 0;
        }

        return rc;
}
EXPORT_SYMBOL_GPL(arch_make_page_accessible);

#endif

#if defined(CONFIG_PROTECTED_VIRTUALIZATION_GUEST) || IS_ENABLED(CONFIG_KVM)
static ssize_t uv_query_facilities(struct kobject *kobj,
                                   struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n%lx\n%lx\n%lx\n",
                          uv_info.inst_calls_list[0],
                          uv_info.inst_calls_list[1],
                          uv_info.inst_calls_list[2],
                          uv_info.inst_calls_list[3]);
}

static struct kobj_attribute uv_query_facilities_attr =
        __ATTR(facilities, 0444, uv_query_facilities, NULL);

static ssize_t uv_query_supp_se_hdr_ver(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.supp_se_hdr_ver);
}

static struct kobj_attribute uv_query_supp_se_hdr_ver_attr =
        __ATTR(supp_se_hdr_ver, 0444, uv_query_supp_se_hdr_ver, NULL);

static ssize_t uv_query_supp_se_hdr_pcf(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.supp_se_hdr_pcf);
}

static struct kobj_attribute uv_query_supp_se_hdr_pcf_attr =
        __ATTR(supp_se_hdr_pcf, 0444, uv_query_supp_se_hdr_pcf, NULL);

static ssize_t uv_query_dump_cpu_len(struct kobject *kobj,
                                     struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.guest_cpu_stor_len);
}

static struct kobj_attribute uv_query_dump_cpu_len_attr =
        __ATTR(uv_query_dump_cpu_len, 0444, uv_query_dump_cpu_len, NULL);

static ssize_t uv_query_dump_storage_state_len(struct kobject *kobj,
                                               struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.conf_dump_storage_state_len);
}

static struct kobj_attribute uv_query_dump_storage_state_len_attr =
        __ATTR(dump_storage_state_len, 0444, uv_query_dump_storage_state_len, NULL);

static ssize_t uv_query_dump_finalize_len(struct kobject *kobj,
                                          struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.conf_dump_finalize_len);
}

static struct kobj_attribute uv_query_dump_finalize_len_attr =
        __ATTR(dump_finalize_len, 0444, uv_query_dump_finalize_len, NULL);

static ssize_t uv_query_feature_indications(struct kobject *kobj,
                                            struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.uv_feature_indications);
}

static struct kobj_attribute uv_query_feature_indications_attr =
        __ATTR(feature_indications, 0444, uv_query_feature_indications, NULL);

static ssize_t uv_query_max_guest_cpus(struct kobject *kobj,
                                       struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%d\n", uv_info.max_guest_cpu_id + 1);
}

static struct kobj_attribute uv_query_max_guest_cpus_attr =
        __ATTR(max_cpus, 0444, uv_query_max_guest_cpus, NULL);

static ssize_t uv_query_max_guest_vms(struct kobject *kobj,
                                      struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%d\n", uv_info.max_num_sec_conf);
}

static struct kobj_attribute uv_query_max_guest_vms_attr =
        __ATTR(max_guests, 0444, uv_query_max_guest_vms, NULL);

static ssize_t uv_query_max_guest_addr(struct kobject *kobj,
                                       struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.max_sec_stor_addr);
}

static struct kobj_attribute uv_query_max_guest_addr_attr =
        __ATTR(max_address, 0444, uv_query_max_guest_addr, NULL);

static ssize_t uv_query_supp_att_req_hdr_ver(struct kobject *kobj,
                                             struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.supp_att_req_hdr_ver);
}

static struct kobj_attribute uv_query_supp_att_req_hdr_ver_attr =
        __ATTR(supp_att_req_hdr_ver, 0444, uv_query_supp_att_req_hdr_ver, NULL);

static ssize_t uv_query_supp_att_pflags(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.supp_att_pflags);
}

static struct kobj_attribute uv_query_supp_att_pflags_attr =
        __ATTR(supp_att_pflags, 0444, uv_query_supp_att_pflags, NULL);

static ssize_t uv_query_supp_add_secret_req_ver(struct kobject *kobj,
                                                struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.supp_add_secret_req_ver);
}

static struct kobj_attribute uv_query_supp_add_secret_req_ver_attr =
        __ATTR(supp_add_secret_req_ver, 0444, uv_query_supp_add_secret_req_ver, NULL);

static ssize_t uv_query_supp_add_secret_pcf(struct kobject *kobj,
                                            struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.supp_add_secret_pcf);
}

static struct kobj_attribute uv_query_supp_add_secret_pcf_attr =
        __ATTR(supp_add_secret_pcf, 0444, uv_query_supp_add_secret_pcf, NULL);

static ssize_t uv_query_supp_secret_types(struct kobject *kobj,
                                          struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%lx\n", uv_info.supp_secret_types);
}

static struct kobj_attribute uv_query_supp_secret_types_attr =
        __ATTR(supp_secret_types, 0444, uv_query_supp_secret_types, NULL);

static ssize_t uv_query_max_secrets(struct kobject *kobj,
                                    struct kobj_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%d\n", uv_info.max_secrets);
}

static struct kobj_attribute uv_query_max_secrets_attr =
        __ATTR(max_secrets, 0444, uv_query_max_secrets, NULL);

static struct attribute *uv_query_attrs[] = {
        &uv_query_facilities_attr.attr,
        &uv_query_feature_indications_attr.attr,
        &uv_query_max_guest_cpus_attr.attr,
        &uv_query_max_guest_vms_attr.attr,
        &uv_query_max_guest_addr_attr.attr,
        &uv_query_supp_se_hdr_ver_attr.attr,
        &uv_query_supp_se_hdr_pcf_attr.attr,
        &uv_query_dump_storage_state_len_attr.attr,
        &uv_query_dump_finalize_len_attr.attr,
        &uv_query_dump_cpu_len_attr.attr,
        &uv_query_supp_att_req_hdr_ver_attr.attr,
        &uv_query_supp_att_pflags_attr.attr,
        &uv_query_supp_add_secret_req_ver_attr.attr,
        &uv_query_supp_add_secret_pcf_attr.attr,
        &uv_query_supp_secret_types_attr.attr,
        &uv_query_max_secrets_attr.attr,
        NULL,
};

static struct attribute_group uv_query_attr_group = {
        .attrs = uv_query_attrs,
};

static ssize_t uv_is_prot_virt_guest(struct kobject *kobj,
                                     struct kobj_attribute *attr, char *buf)
{
        int val = 0;

#ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
        val = prot_virt_guest;
#endif
        return sysfs_emit(buf, "%d\n", val);
}

static ssize_t uv_is_prot_virt_host(struct kobject *kobj,
                                    struct kobj_attribute *attr, char *buf)
{
        int val = 0;

#if IS_ENABLED(CONFIG_KVM)
        val = prot_virt_host;
#endif

        return sysfs_emit(buf, "%d\n", val);
}

static struct kobj_attribute uv_prot_virt_guest =
        __ATTR(prot_virt_guest, 0444, uv_is_prot_virt_guest, NULL);

static struct kobj_attribute uv_prot_virt_host =
        __ATTR(prot_virt_host, 0444, uv_is_prot_virt_host, NULL);

static const struct attribute *uv_prot_virt_attrs[] = {
        &uv_prot_virt_guest.attr,
        &uv_prot_virt_host.attr,
        NULL,
};

static struct kset *uv_query_kset;
static struct kobject *uv_kobj;

static int __init uv_info_init(void)
{
        int rc = -ENOMEM;

        if (!test_facility(158))
                return 0;

        uv_kobj = kobject_create_and_add("uv", firmware_kobj);
        if (!uv_kobj)
                return -ENOMEM;

        rc = sysfs_create_files(uv_kobj, uv_prot_virt_attrs);
        if (rc)
                goto out_kobj;

        uv_query_kset = kset_create_and_add("query", NULL, uv_kobj);
        if (!uv_query_kset) {
                rc = -ENOMEM;
                goto out_ind_files;
        }

        rc = sysfs_create_group(&uv_query_kset->kobj, &uv_query_attr_group);
        if (!rc)
                return 0;

        kset_unregister(uv_query_kset);
out_ind_files:
        sysfs_remove_files(uv_kobj, uv_prot_virt_attrs);
out_kobj:
        kobject_del(uv_kobj);
        kobject_put(uv_kobj);
        return rc;
}
device_initcall(uv_info_init);
#endif