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[mirror_ubuntu-focal-kernel.git] / drivers / s390 / cio / vfio_ccw_cp.c

// SPDX-License-Identifier: GPL-2.0
/*
 * channel program interfaces
 *
 * Copyright IBM Corp. 2017
 *
 * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
 *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
 */

#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/iommu.h>
#include <linux/vfio.h>
#include <asm/idals.h>

#include "vfio_ccw_cp.h"

/*
 * Max length for ccw chain.
 * XXX: Limit to 256, need to check more?
 */
#define CCWCHAIN_LEN_MAX        256

struct pfn_array {
        unsigned long           pa_iova;
        unsigned long           *pa_iova_pfn;
        unsigned long           *pa_pfn;
        int                     pa_nr;
};

struct pfn_array_table {
        struct pfn_array        *pat_pa;
        int                     pat_nr;
};

struct ccwchain {
        struct list_head        next;
        struct ccw1             *ch_ccw;
        /* Guest physical address of the current chain. */
        u64                     ch_iova;
        /* Count of the valid ccws in chain. */
        int                     ch_len;
        /* Pinned PAGEs for the original data. */
        struct pfn_array_table  *ch_pat;
};

/*
 * pfn_array_pin() - pin user pages in memory
 * @pa: pfn_array on which to perform the operation
 * @mdev: the mediated device to perform pin/unpin operations
 *
 * Attempt to pin user pages in memory.
 *
 * Usage of pfn_array:
 * @pa->pa_iova     starting guest physical I/O address. Assigned by caller.
 * @pa->pa_iova_pfn array that stores PFNs of the pages need to pin. Allocated
 *                  by caller.
 * @pa->pa_pfn      array that receives PFNs of the pages pinned. Allocated by
 *                  caller.
 * @pa->pa_nr       number of pages from @pa->pa_iova to pin. Assigned by
 *                  caller.
 *                  number of pages pinned. Assigned by callee.
 *
 * Returns:
 *   Number of pages pinned on success.
 *   If @pa->pa_nr is 0 or negative, returns 0.
 *   If no pages were pinned, returns -errno.
 */
static int pfn_array_pin(struct pfn_array *pa, struct device *mdev)
{
        int i, ret;

        if (pa->pa_nr <= 0) {
                pa->pa_nr = 0;
                return 0;
        }

        pa->pa_iova_pfn[0] = pa->pa_iova >> PAGE_SHIFT;
        for (i = 1; i < pa->pa_nr; i++)
                pa->pa_iova_pfn[i] = pa->pa_iova_pfn[i - 1] + 1;

        ret = vfio_pin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr,
                             IOMMU_READ | IOMMU_WRITE, pa->pa_pfn);

        if (ret > 0 && ret != pa->pa_nr) {
                vfio_unpin_pages(mdev, pa->pa_iova_pfn, ret);
                pa->pa_nr = 0;
                return 0;
        }

        return ret;
}

/* Unpin the pages before releasing the memory. */
static void pfn_array_unpin_free(struct pfn_array *pa, struct device *mdev)
{
        vfio_unpin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr);
        pa->pa_nr = 0;
        kfree(pa->pa_iova_pfn);
}

/* Alloc memory for PFNs, then pin pages with them. */
static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
                               u64 iova, unsigned int len)
{
        int ret = 0;

        if (!len || pa->pa_nr)
                return -EINVAL;

        pa->pa_iova = iova;

        pa->pa_nr = ((iova & ~PAGE_MASK) + len + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
        if (!pa->pa_nr)
                return -EINVAL;

        pa->pa_iova_pfn = kcalloc(pa->pa_nr,
                                  sizeof(*pa->pa_iova_pfn) +
                                  sizeof(*pa->pa_pfn),
                                  GFP_KERNEL);
        if (unlikely(!pa->pa_iova_pfn))
                return -ENOMEM;
        pa->pa_pfn = pa->pa_iova_pfn + pa->pa_nr;

        ret = pfn_array_pin(pa, mdev);

        if (ret > 0)
                return ret;
        else if (!ret)
                ret = -EINVAL;

        kfree(pa->pa_iova_pfn);

        return ret;
}

static int pfn_array_table_init(struct pfn_array_table *pat, int nr)
{
        pat->pat_pa = kcalloc(nr, sizeof(*pat->pat_pa), GFP_KERNEL);
        if (unlikely(ZERO_OR_NULL_PTR(pat->pat_pa))) {
                pat->pat_nr = 0;
                return -ENOMEM;
        }

        pat->pat_nr = nr;

        return 0;
}

static void pfn_array_table_unpin_free(struct pfn_array_table *pat,
                                       struct device *mdev)
{
        int i;

        for (i = 0; i < pat->pat_nr; i++)
                pfn_array_unpin_free(pat->pat_pa + i, mdev);

        if (pat->pat_nr) {
                kfree(pat->pat_pa);
                pat->pat_pa = NULL;
                pat->pat_nr = 0;
        }
}

static bool pfn_array_table_iova_pinned(struct pfn_array_table *pat,
                                        unsigned long iova)
{
        struct pfn_array *pa = pat->pat_pa;
        unsigned long iova_pfn = iova >> PAGE_SHIFT;
        int i, j;

        for (i = 0; i < pat->pat_nr; i++, pa++)
                for (j = 0; j < pa->pa_nr; j++)
                        if (pa->pa_iova_pfn[i] == iova_pfn)
                                return true;

        return false;
}
/* Create the list idal words for a pfn_array_table. */
static inline void pfn_array_table_idal_create_words(
        struct pfn_array_table *pat,
        unsigned long *idaws)
{
        struct pfn_array *pa;
        int i, j, k;

        /*
         * Idal words (execept the first one) rely on the memory being 4k
         * aligned. If a user virtual address is 4K aligned, then it's
         * corresponding kernel physical address will also be 4K aligned. Thus
         * there will be no problem here to simply use the phys to create an
         * idaw.
         */
        k = 0;
        for (i = 0; i < pat->pat_nr; i++) {
                pa = pat->pat_pa + i;
                for (j = 0; j < pa->pa_nr; j++) {
                        idaws[k] = pa->pa_pfn[j] << PAGE_SHIFT;
                        if (k == 0)
                                idaws[k] += pa->pa_iova & (PAGE_SIZE - 1);
                        k++;
                }
        }
}


/*
 * Within the domain (@mdev), copy @n bytes from a guest physical
 * address (@iova) to a host physical address (@to).
 */
static long copy_from_iova(struct device *mdev,
                           void *to, u64 iova,
                           unsigned long n)
{
        struct pfn_array pa = {0};
        u64 from;
        int i, ret;
        unsigned long l, m;

        ret = pfn_array_alloc_pin(&pa, mdev, iova, n);
        if (ret <= 0)
                return ret;

        l = n;
        for (i = 0; i < pa.pa_nr; i++) {
                from = pa.pa_pfn[i] << PAGE_SHIFT;
                m = PAGE_SIZE;
                if (i == 0) {
                        from += iova & (PAGE_SIZE - 1);
                        m -= iova & (PAGE_SIZE - 1);
                }

                m = min(l, m);
                memcpy(to + (n - l), (void *)from, m);

                l -= m;
                if (l == 0)
                        break;
        }

        pfn_array_unpin_free(&pa, mdev);

        return l;
}

static long copy_ccw_from_iova(struct channel_program *cp,
                               struct ccw1 *to, u64 iova,
                               unsigned long len)
{
        struct ccw0 ccw0;
        struct ccw1 *pccw1;
        int ret;
        int i;

        ret = copy_from_iova(cp->mdev, to, iova, len * sizeof(struct ccw1));
        if (ret)
                return ret;

        if (!cp->orb.cmd.fmt) {
                pccw1 = to;
                for (i = 0; i < len; i++) {
                        ccw0 = *(struct ccw0 *)pccw1;
                        if ((pccw1->cmd_code & 0x0f) == CCW_CMD_TIC) {
                                pccw1->cmd_code = CCW_CMD_TIC;
                                pccw1->flags = 0;
                                pccw1->count = 0;
                        } else {
                                pccw1->cmd_code = ccw0.cmd_code;
                                pccw1->flags = ccw0.flags;
                                pccw1->count = ccw0.count;
                        }
                        pccw1->cda = ccw0.cda;
                        pccw1++;
                }
        }

        return ret;
}

/*
 * Helpers to operate ccwchain.
 */
#define ccw_is_test(_ccw) (((_ccw)->cmd_code & 0x0F) == 0)

#define ccw_is_noop(_ccw) ((_ccw)->cmd_code == CCW_CMD_NOOP)

#define ccw_is_tic(_ccw) ((_ccw)->cmd_code == CCW_CMD_TIC)

#define ccw_is_idal(_ccw) ((_ccw)->flags & CCW_FLAG_IDA)


#define ccw_is_chain(_ccw) ((_ccw)->flags & (CCW_FLAG_CC | CCW_FLAG_DC))

static struct ccwchain *ccwchain_alloc(struct channel_program *cp, int len)
{
        struct ccwchain *chain;
        void *data;
        size_t size;

        /* Make ccw address aligned to 8. */
        size = ((sizeof(*chain) + 7L) & -8L) +
                sizeof(*chain->ch_ccw) * len +
                sizeof(*chain->ch_pat) * len;
        chain = kzalloc(size, GFP_DMA | GFP_KERNEL);
        if (!chain)
                return NULL;

        data = (u8 *)chain + ((sizeof(*chain) + 7L) & -8L);
        chain->ch_ccw = (struct ccw1 *)data;

        data = (u8 *)(chain->ch_ccw) + sizeof(*chain->ch_ccw) * len;
        chain->ch_pat = (struct pfn_array_table *)data;

        chain->ch_len = len;

        list_add_tail(&chain->next, &cp->ccwchain_list);

        return chain;
}

static void ccwchain_free(struct ccwchain *chain)
{
        list_del(&chain->next);
        kfree(chain);
}

/* Free resource for a ccw that allocated memory for its cda. */
static void ccwchain_cda_free(struct ccwchain *chain, int idx)
{
        struct ccw1 *ccw = chain->ch_ccw + idx;

        if (!ccw->count)
                return;

        kfree((void *)(u64)ccw->cda);
}

/* Unpin the pages then free the memory resources. */
static void cp_unpin_free(struct channel_program *cp)
{
        struct ccwchain *chain, *temp;
        int i;

        list_for_each_entry_safe(chain, temp, &cp->ccwchain_list, next) {
                for (i = 0; i < chain->ch_len; i++) {
                        pfn_array_table_unpin_free(chain->ch_pat + i,
                                                   cp->mdev);
                        ccwchain_cda_free(chain, i);
                }
                ccwchain_free(chain);
        }
}

/**
 * ccwchain_calc_length - calculate the length of the ccw chain.
 * @iova: guest physical address of the target ccw chain
 * @cp: channel_program on which to perform the operation
 *
 * This is the chain length not considering any TICs.
 * You need to do a new round for each TIC target.
 *
 * Returns: the length of the ccw chain or -errno.
 */
static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
{
        struct ccw1 *ccw, *p;
        int cnt;

        /*
         * Copy current chain from guest to host kernel.
         * Currently the chain length is limited to CCWCHAIN_LEN_MAX (256).
         * So copying 2K is enough (safe).
         */
        p = ccw = kcalloc(CCWCHAIN_LEN_MAX, sizeof(*ccw), GFP_KERNEL);
        if (!ccw)
                return -ENOMEM;

        cnt = copy_ccw_from_iova(cp, ccw, iova, CCWCHAIN_LEN_MAX);
        if (cnt) {
                kfree(ccw);
                return cnt;
        }

        cnt = 0;
        do {
                cnt++;

                if ((!ccw_is_chain(ccw)) && (!ccw_is_tic(ccw)))
                        break;

                ccw++;
        } while (cnt < CCWCHAIN_LEN_MAX + 1);

        if (cnt == CCWCHAIN_LEN_MAX + 1)
                cnt = -EINVAL;

        kfree(p);
        return cnt;
}

static int tic_target_chain_exists(struct ccw1 *tic, struct channel_program *cp)
{
        struct ccwchain *chain;
        u32 ccw_head, ccw_tail;

        list_for_each_entry(chain, &cp->ccwchain_list, next) {
                ccw_head = chain->ch_iova;
                ccw_tail = ccw_head + (chain->ch_len - 1) * sizeof(struct ccw1);

                if ((ccw_head <= tic->cda) && (tic->cda <= ccw_tail))
                        return 1;
        }

        return 0;
}

static int ccwchain_loop_tic(struct ccwchain *chain,
                             struct channel_program *cp);

static int ccwchain_handle_tic(struct ccw1 *tic, struct channel_program *cp)
{
        struct ccwchain *chain;
        int len, ret;

        /* May transfer to an existing chain. */
        if (tic_target_chain_exists(tic, cp))
                return 0;

        /* Get chain length. */
        len = ccwchain_calc_length(tic->cda, cp);
        if (len < 0)
                return len;

        /* Need alloc a new chain for this one. */
        chain = ccwchain_alloc(cp, len);
        if (!chain)
                return -ENOMEM;
        chain->ch_iova = tic->cda;

        /* Copy the new chain from user. */
        ret = copy_ccw_from_iova(cp, chain->ch_ccw, tic->cda, len);
        if (ret) {
                ccwchain_free(chain);
                return ret;
        }

        /* Loop for tics on this new chain. */
        return ccwchain_loop_tic(chain, cp);
}

/* Loop for TICs. */
static int ccwchain_loop_tic(struct ccwchain *chain, struct channel_program *cp)
{
        struct ccw1 *tic;
        int i, ret;

        for (i = 0; i < chain->ch_len; i++) {
                tic = chain->ch_ccw + i;

                if (!ccw_is_tic(tic))
                        continue;

                ret = ccwchain_handle_tic(tic, cp);
                if (ret)
                        return ret;
        }

        return 0;
}

static int ccwchain_fetch_tic(struct ccwchain *chain,
                              int idx,
                              struct channel_program *cp)
{
        struct ccw1 *ccw = chain->ch_ccw + idx;
        struct ccwchain *iter;
        u32 ccw_head, ccw_tail;

        list_for_each_entry(iter, &cp->ccwchain_list, next) {
                ccw_head = iter->ch_iova;
                ccw_tail = ccw_head + (iter->ch_len - 1) * sizeof(struct ccw1);

                if ((ccw_head <= ccw->cda) && (ccw->cda <= ccw_tail)) {
                        ccw->cda = (__u32) (addr_t) (((char *)iter->ch_ccw) +
                                                     (ccw->cda - ccw_head));
                        return 0;
                }
        }

        return -EFAULT;
}

static int ccwchain_fetch_direct(struct ccwchain *chain,
                                 int idx,
                                 struct channel_program *cp)
{
        struct ccw1 *ccw;
        struct pfn_array_table *pat;
        unsigned long *idaws;
        int idaw_nr;

        ccw = chain->ch_ccw + idx;

        /*
         * Pin data page(s) in memory.
         * The number of pages actually is the count of the idaws which will be
         * needed when translating a direct ccw to a idal ccw.
         */
        pat = chain->ch_pat + idx;
        if (pfn_array_table_init(pat, 1))
                return -ENOMEM;
        idaw_nr = pfn_array_alloc_pin(pat->pat_pa, cp->mdev,
                                      ccw->cda, ccw->count);
        if (idaw_nr < 0)
                return idaw_nr;

        /* Translate this direct ccw to a idal ccw. */
        idaws = kcalloc(idaw_nr, sizeof(*idaws), GFP_DMA | GFP_KERNEL);
        if (!idaws) {
                pfn_array_table_unpin_free(pat, cp->mdev);
                return -ENOMEM;
        }
        ccw->cda = (__u32) virt_to_phys(idaws);
        ccw->flags |= CCW_FLAG_IDA;

        pfn_array_table_idal_create_words(pat, idaws);

        return 0;
}

static int ccwchain_fetch_idal(struct ccwchain *chain,
                               int idx,
                               struct channel_program *cp)
{
        struct ccw1 *ccw;
        struct pfn_array_table *pat;
        unsigned long *idaws;
        u64 idaw_iova;
        unsigned int idaw_nr, idaw_len;
        int i, ret;

        ccw = chain->ch_ccw + idx;

        /* Calculate size of idaws. */
        ret = copy_from_iova(cp->mdev, &idaw_iova, ccw->cda, sizeof(idaw_iova));
        if (ret)
                return ret;
        idaw_nr = idal_nr_words((void *)(idaw_iova), ccw->count);
        idaw_len = idaw_nr * sizeof(*idaws);

        /* Pin data page(s) in memory. */
        pat = chain->ch_pat + idx;
        ret = pfn_array_table_init(pat, idaw_nr);
        if (ret)
                return ret;

        /* Translate idal ccw to use new allocated idaws. */
        idaws = kzalloc(idaw_len, GFP_DMA | GFP_KERNEL);
        if (!idaws) {
                ret = -ENOMEM;
                goto out_unpin;
        }

        ret = copy_from_iova(cp->mdev, idaws, ccw->cda, idaw_len);
        if (ret)
                goto out_free_idaws;

        ccw->cda = virt_to_phys(idaws);

        for (i = 0; i < idaw_nr; i++) {
                idaw_iova = *(idaws + i);
                if (IS_ERR_VALUE(idaw_iova)) {
                        ret = -EFAULT;
                        goto out_free_idaws;
                }

                ret = pfn_array_alloc_pin(pat->pat_pa + i, cp->mdev,
                                          idaw_iova, 1);
                if (ret < 0)
                        goto out_free_idaws;
        }

        pfn_array_table_idal_create_words(pat, idaws);

        return 0;

out_free_idaws:
        kfree(idaws);
out_unpin:
        pfn_array_table_unpin_free(pat, cp->mdev);
        return ret;
}

/*
 * Fetch one ccw.
 * To reduce memory copy, we'll pin the cda page in memory,
 * and to get rid of the cda 2G limitiaion of ccw1, we'll translate
 * direct ccws to idal ccws.
 */
static int ccwchain_fetch_one(struct ccwchain *chain,
                              int idx,
                              struct channel_program *cp)
{
        struct ccw1 *ccw = chain->ch_ccw + idx;

        if (ccw_is_test(ccw) || ccw_is_noop(ccw))
                return 0;

        if (ccw_is_tic(ccw))
                return ccwchain_fetch_tic(chain, idx, cp);

        if (ccw_is_idal(ccw))
                return ccwchain_fetch_idal(chain, idx, cp);

        return ccwchain_fetch_direct(chain, idx, cp);
}

/**
 * cp_init() - allocate ccwchains for a channel program.
 * @cp: channel_program on which to perform the operation
 * @mdev: the mediated device to perform pin/unpin operations
 * @orb: control block for the channel program from the guest
 *
 * This creates one or more ccwchain(s), and copies the raw data of
 * the target channel program from @orb->cmd.iova to the new ccwchain(s).
 *
 * Limitations:
 * 1. Supports only prefetch enabled mode.
 * 2. Supports idal(c64) ccw chaining.
 * 3. Supports 4k idaw.
 *
 * Returns:
 *   %0 on success and a negative error value on failure.
 */
int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
{
        u64 iova = orb->cmd.cpa;
        struct ccwchain *chain;
        int len, ret;

        /*
         * XXX:
         * Only support prefetch enable mode now.
         * Only support 64bit addressing idal.
         * Only support 4k IDAW.
         */
        if (!orb->cmd.pfch || !orb->cmd.c64 || orb->cmd.i2k)
                return -EOPNOTSUPP;

        INIT_LIST_HEAD(&cp->ccwchain_list);
        memcpy(&cp->orb, orb, sizeof(*orb));
        cp->mdev = mdev;

        /* Get chain length. */
        len = ccwchain_calc_length(iova, cp);
        if (len < 0)
                return len;

        /* Alloc mem for the head chain. */
        chain = ccwchain_alloc(cp, len);
        if (!chain)
                return -ENOMEM;
        chain->ch_iova = iova;

        /* Copy the head chain from guest. */
        ret = copy_ccw_from_iova(cp, chain->ch_ccw, iova, len);
        if (ret) {
                ccwchain_free(chain);
                return ret;
        }

        /* Now loop for its TICs. */
        ret = ccwchain_loop_tic(chain, cp);
        if (ret)
                cp_unpin_free(cp);

        return ret;
}


/**
 * cp_free() - free resources for channel program.
 * @cp: channel_program on which to perform the operation
 *
 * This unpins the memory pages and frees the memory space occupied by
 * @cp, which must have been returned by a previous call to cp_init().
 * Otherwise, undefined behavior occurs.
 */
void cp_free(struct channel_program *cp)
{
        cp_unpin_free(cp);
}

/**
 * cp_prefetch() - translate a guest physical address channel program to
 *                 a real-device runnable channel program.
 * @cp: channel_program on which to perform the operation
 *
 * This function translates the guest-physical-address channel program
 * and stores the result to ccwchain list. @cp must have been
 * initialized by a previous call with cp_init(). Otherwise, undefined
 * behavior occurs.
 *
 * The S/390 CCW Translation APIS (prefixed by 'cp_') are introduced
 * as helpers to do ccw chain translation inside the kernel. Basically
 * they accept a channel program issued by a virtual machine, and
 * translate the channel program to a real-device runnable channel
 * program.
 *
 * These APIs will copy the ccws into kernel-space buffers, and update
 * the guest phsical addresses with their corresponding host physical
 * addresses.  Then channel I/O device drivers could issue the
 * translated channel program to real devices to perform an I/O
 * operation.
 *
 * These interfaces are designed to support translation only for
 * channel programs, which are generated and formatted by a
 * guest. Thus this will make it possible for things like VFIO to
 * leverage the interfaces to passthrough a channel I/O mediated
 * device in QEMU.
 *
 * We support direct ccw chaining by translating them to idal ccws.
 *
 * Returns:
 *   %0 on success and a negative error value on failure.
 */
int cp_prefetch(struct channel_program *cp)
{
        struct ccwchain *chain;
        int len, idx, ret;

        list_for_each_entry(chain, &cp->ccwchain_list, next) {
                len = chain->ch_len;
                for (idx = 0; idx < len; idx++) {
                        ret = ccwchain_fetch_one(chain, idx, cp);
                        if (ret)
                                return ret;
                }
        }

        return 0;
}

/**
 * cp_get_orb() - get the orb of the channel program
 * @cp: channel_program on which to perform the operation
 * @intparm: new intparm for the returned orb
 * @lpm: candidate value of the logical-path mask for the returned orb
 *
 * This function returns the address of the updated orb of the channel
 * program. Channel I/O device drivers could use this orb to issue a
 * ssch.
 */
union orb *cp_get_orb(struct channel_program *cp, u32 intparm, u8 lpm)
{
        union orb *orb;
        struct ccwchain *chain;
        struct ccw1 *cpa;

        orb = &cp->orb;

        orb->cmd.intparm = intparm;
        orb->cmd.fmt = 1;
        orb->cmd.key = PAGE_DEFAULT_KEY >> 4;

        if (orb->cmd.lpm == 0)
                orb->cmd.lpm = lpm;

        chain = list_first_entry(&cp->ccwchain_list, struct ccwchain, next);
        cpa = chain->ch_ccw;
        orb->cmd.cpa = (__u32) __pa(cpa);

        return orb;
}

/**
 * cp_update_scsw() - update scsw for a channel program.
 * @cp: channel_program on which to perform the operation
 * @scsw: I/O results of the channel program and also the target to be
 *        updated
 *
 * @scsw contains the I/O results of the channel program that pointed
 * to by @cp. However what @scsw->cpa stores is a host physical
 * address, which is meaningless for the guest, which is waiting for
 * the I/O results.
 *
 * This function updates @scsw->cpa to its coressponding guest physical
 * address.
 */
void cp_update_scsw(struct channel_program *cp, union scsw *scsw)
{
        struct ccwchain *chain;
        u32 cpa = scsw->cmd.cpa;
        u32 ccw_head, ccw_tail;

        /*
         * LATER:
         * For now, only update the cmd.cpa part. We may need to deal with
         * other portions of the schib as well, even if we don't return them
         * in the ioctl directly. Path status changes etc.
         */
        list_for_each_entry(chain, &cp->ccwchain_list, next) {
                ccw_head = (u32)(u64)chain->ch_ccw;
                ccw_tail = (u32)(u64)(chain->ch_ccw + chain->ch_len - 1);

                if ((ccw_head <= cpa) && (cpa <= ccw_tail)) {
                        /*
                         * (cpa - ccw_head) is the offset value of the host
                         * physical ccw to its chain head.
                         * Adding this value to the guest physical ccw chain
                         * head gets us the guest cpa.
                         */
                        cpa = chain->ch_iova + (cpa - ccw_head);
                        break;
                }
        }

        scsw->cmd.cpa = cpa;
}

/**
 * cp_iova_pinned() - check if an iova is pinned for a ccw chain.
 * @cmd: ccwchain command on which to perform the operation
 * @iova: the iova to check
 *
 * If the @iova is currently pinned for the ccw chain, return true;
 * else return false.
 */
bool cp_iova_pinned(struct channel_program *cp, u64 iova)
{
        struct ccwchain *chain;
        int i;

        list_for_each_entry(chain, &cp->ccwchain_list, next) {
                for (i = 0; i < chain->ch_len; i++)
                        if (pfn_array_table_iova_pinned(chain->ch_pat + i,
                                                        iova))
                                return true;
        }

        return false;
}