1 files changed, 875 insertions, 0 deletions

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
new file mode 100644
index 000000000..8d1b2771c
--- /dev/null
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -0,0 +1,875 @@
+// 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/ratelimit.h>
+#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"
+
+struct pfn_array {
+	/* Starting guest physical I/O address. */
+	unsigned long		pa_iova;
+	/* Array that stores PFNs of the pages need to pin. */
+	unsigned long		*pa_iova_pfn;
+	/* Array that receives PFNs of the pages pinned. */
+	unsigned long		*pa_pfn;
+	/* Number of pages pinned from @pa_iova. */
+	int			pa_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	*ch_pa;
+};
+
+/*
+ * pfn_array_alloc() - alloc memory for PFNs
+ * @pa: pfn_array on which to perform the operation
+ * @iova: target guest physical address
+ * @len: number of bytes that should be pinned from @iova
+ *
+ * Attempt to allocate memory for PFNs.
+ *
+ * Usage of pfn_array:
+ * We expect (pa_nr == 0) and (pa_iova_pfn == NULL), any field in
+ * this structure will be filled in by this function.
+ *
+ * Returns:
+ *         0 if PFNs are allocated
+ *   -EINVAL if pa->pa_nr is not initially zero, or pa->pa_iova_pfn is not NULL
+ *   -ENOMEM if alloc failed
+ */
+static int pfn_array_alloc(struct pfn_array *pa, u64 iova, unsigned int len)
+{
+	int i;
+
+	if (pa->pa_nr || pa->pa_iova_pfn)
+		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)) {
+		pa->pa_nr = 0;
+		return -ENOMEM;
+	}
+	pa->pa_pfn = pa->pa_iova_pfn + pa->pa_nr;
+
+	pa->pa_iova_pfn[0] = pa->pa_iova >> PAGE_SHIFT;
+	pa->pa_pfn[0] = -1ULL;
+	for (i = 1; i < pa->pa_nr; i++) {
+		pa->pa_iova_pfn[i] = pa->pa_iova_pfn[i - 1] + 1;
+		pa->pa_pfn[i] = -1ULL;
+	}
+
+	return 0;
+}
+
+/*
+ * pfn_array_pin() - Pin user pages in memory
+ * @pa: pfn_array on which to perform the operation
+ * @mdev: the mediated device to perform pin operations
+ *
+ * Returns number of pages pinned upon success.
+ * If the pin request partially succeeds, or fails completely,
+ * all pages are left unpinned and a negative error value is returned.
+ */
+static int pfn_array_pin(struct pfn_array *pa, struct device *mdev)
+{
+	int ret = 0;
+
+	ret = vfio_pin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr,
+			     IOMMU_READ | IOMMU_WRITE, pa->pa_pfn);
+
+	if (ret < 0) {
+		goto err_out;
+	} else if (ret > 0 && ret != pa->pa_nr) {
+		vfio_unpin_pages(mdev, pa->pa_iova_pfn, ret);
+		ret = -EINVAL;
+		goto err_out;
+	}
+
+	return ret;
+
+err_out:
+	pa->pa_nr = 0;
+
+	return ret;
+}
+
+/* Unpin the pages before releasing the memory. */
+static void pfn_array_unpin_free(struct pfn_array *pa, struct device *mdev)
+{
+	/* Only unpin if any pages were pinned to begin with */
+	if (pa->pa_nr)
+		vfio_unpin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr);
+	pa->pa_nr = 0;
+	kfree(pa->pa_iova_pfn);
+}
+
+static bool pfn_array_iova_pinned(struct pfn_array *pa, unsigned long iova)
+{
+	unsigned long iova_pfn = iova >> PAGE_SHIFT;
+	int i;
+
+	for (i = 0; i < pa->pa_nr; i++)
+		if (pa->pa_iova_pfn[i] == iova_pfn)
+			return true;
+
+	return false;
+}
+/* Create the list of IDAL words for a pfn_array. */
+static inline void pfn_array_idal_create_words(
+	struct pfn_array *pa,
+	unsigned long *idaws)
+{
+	int i;
+
+	/*
+	 * 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.
+	 */
+
+	for (i = 0; i < pa->pa_nr; i++)
+		idaws[i] = pa->pa_pfn[i] << PAGE_SHIFT;
+
+	/* Adjust the first IDAW, since it may not start on a page boundary */
+	idaws[0] += pa->pa_iova & (PAGE_SIZE - 1);
+}
+
+static void convert_ccw0_to_ccw1(struct ccw1 *source, unsigned long len)
+{
+	struct ccw0 ccw0;
+	struct ccw1 *pccw1 = source;
+	int i;
+
+	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++;
+	}
+}
+
+/*
+ * 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(&pa, iova, n);
+	if (ret < 0)
+		return ret;
+
+	ret = pfn_array_pin(&pa, mdev);
+	if (ret < 0) {
+		pfn_array_unpin_free(&pa, mdev);
+		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;
+}
+
+/*
+ * Helpers to operate ccwchain.
+ */
+#define ccw_is_read(_ccw) (((_ccw)->cmd_code & 0x03) == 0x02)
+#define ccw_is_read_backward(_ccw) (((_ccw)->cmd_code & 0x0F) == 0x0C)
+#define ccw_is_sense(_ccw) (((_ccw)->cmd_code & 0x0F) == CCW_CMD_BASIC_SENSE)
+
+#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_skip(_ccw) ((_ccw)->flags & CCW_FLAG_SKIP)
+
+#define ccw_is_chain(_ccw) ((_ccw)->flags & (CCW_FLAG_CC | CCW_FLAG_DC))
+
+/*
+ * ccw_does_data_transfer()
+ *
+ * Determine whether a CCW will move any data, such that the guest pages
+ * would need to be pinned before performing the I/O.
+ *
+ * Returns 1 if yes, 0 if no.
+ */
+static inline int ccw_does_data_transfer(struct ccw1 *ccw)
+{
+	/* If the count field is zero, then no data will be transferred */
+	if (ccw->count == 0)
+		return 0;
+
+	/* If the command is a NOP, then no data will be transferred */
+	if (ccw_is_noop(ccw))
+		return 0;
+
+	/* If the skip flag is off, then data will be transferred */
+	if (!ccw_is_skip(ccw))
+		return 1;
+
+	/*
+	 * If the skip flag is on, it is only meaningful if the command
+	 * code is a read, read backward, sense, or sense ID.  In those
+	 * cases, no data will be transferred.
+	 */
+	if (ccw_is_read(ccw) || ccw_is_read_backward(ccw))
+		return 0;
+
+	if (ccw_is_sense(ccw))
+		return 0;
+
+	/* The skip flag is on, but it is ignored for this command code. */
+	return 1;
+}
+
+/*
+ * is_cpa_within_range()
+ *
+ * @cpa: channel program address being questioned
+ * @head: address of the beginning of a CCW chain
+ * @len: number of CCWs within the chain
+ *
+ * Determine whether the address of a CCW (whether a new chain,
+ * or the target of a TIC) falls within a range (including the end points).
+ *
+ * Returns 1 if yes, 0 if no.
+ */
+static inline int is_cpa_within_range(u32 cpa, u32 head, int len)
+{
+	u32 tail = head + (len - 1) * sizeof(struct ccw1);
+
+	return (head <= cpa && cpa <= tail);
+}
+
+static inline int is_tic_within_range(struct ccw1 *ccw, u32 head, int len)
+{
+	if (!ccw_is_tic(ccw))
+		return 0;
+
+	return is_cpa_within_range(ccw->cda, head, len);
+}
+
+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_pa) * 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_pa = (struct pfn_array *)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_is_tic(ccw))
+		return;
+
+	kfree((void *)(u64)ccw->cda);
+}
+
+/**
+ * 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.
+ *
+ * The program is also validated for absence of not yet supported
+ * indirect data addressing scenarios.
+ *
+ * Returns: the length of the ccw chain or -errno.
+ */
+static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
+{
+	struct ccw1 *ccw = cp->guest_cp;
+	int cnt = 0;
+
+	do {
+		cnt++;
+
+		/*
+		 * As we don't want to fail direct addressing even if the
+		 * orb specified one of the unsupported formats, we defer
+		 * checking for IDAWs in unsupported formats to here.
+		 */
+		if ((!cp->orb.cmd.c64 || cp->orb.cmd.i2k) && ccw_is_idal(ccw))
+			return -EOPNOTSUPP;
+
+		/*
+		 * We want to keep counting if the current CCW has the
+		 * command-chaining flag enabled, or if it is a TIC CCW
+		 * that loops back into the current chain.  The latter
+		 * is used for device orientation, where the CCW PRIOR to
+		 * the TIC can either jump to the TIC or a CCW immediately
+		 * after the TIC, depending on the results of its operation.
+		 */
+		if (!ccw_is_chain(ccw) && !is_tic_within_range(ccw, iova, cnt))
+			break;
+
+		ccw++;
+	} while (cnt < CCWCHAIN_LEN_MAX + 1);
+
+	if (cnt == CCWCHAIN_LEN_MAX + 1)
+		cnt = -EINVAL;
+
+	return cnt;
+}
+
+static int tic_target_chain_exists(struct ccw1 *tic, struct channel_program *cp)
+{
+	struct ccwchain *chain;
+	u32 ccw_head;
+
+	list_for_each_entry(chain, &cp->ccwchain_list, next) {
+		ccw_head = chain->ch_iova;
+		if (is_cpa_within_range(tic->cda, ccw_head, chain->ch_len))
+			return 1;
+	}
+
+	return 0;
+}
+
+static int ccwchain_loop_tic(struct ccwchain *chain,
+			     struct channel_program *cp);
+
+static int ccwchain_handle_ccw(u32 cda, struct channel_program *cp)
+{
+	struct ccwchain *chain;
+	int len, ret;
+
+	/* Copy 2K (the most we support today) of possible CCWs */
+	len = copy_from_iova(cp->mdev, cp->guest_cp, cda,
+			     CCWCHAIN_LEN_MAX * sizeof(struct ccw1));
+	if (len)
+		return len;
+
+	/* Convert any Format-0 CCWs to Format-1 */
+	if (!cp->orb.cmd.fmt)
+		convert_ccw0_to_ccw1(cp->guest_cp, CCWCHAIN_LEN_MAX);
+
+	/* Count the CCWs in the current chain */
+	len = ccwchain_calc_length(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 = cda;
+
+	/* Copy the actual CCWs into the new chain */
+	memcpy(chain->ch_ccw, cp->guest_cp, len * sizeof(struct ccw1));
+
+	/* Loop for tics on this new chain. */
+	ret = ccwchain_loop_tic(chain, cp);
+
+	if (ret)
+		ccwchain_free(chain);
+
+	return ret;
+}
+
+/* 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;
+
+		/* May transfer to an existing chain. */
+		if (tic_target_chain_exists(tic, cp))
+			continue;
+
+		/* Build a ccwchain for the next segment */
+		ret = ccwchain_handle_ccw(tic->cda, 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;
+
+	list_for_each_entry(iter, &cp->ccwchain_list, next) {
+		ccw_head = iter->ch_iova;
+		if (is_cpa_within_range(ccw->cda, ccw_head, iter->ch_len)) {
+			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 *pa;
+	u64 iova;
+	unsigned long *idaws;
+	int ret;
+	int bytes = 1;
+	int idaw_nr, idal_len;
+	int i;
+
+	ccw = chain->ch_ccw + idx;
+
+	if (ccw->count)
+		bytes = ccw->count;
+
+	/* Calculate size of IDAL */
+	if (ccw_is_idal(ccw)) {
+		/* Read first IDAW to see if it's 4K-aligned or not. */
+		/* All subsequent IDAws will be 4K-aligned. */
+		ret = copy_from_iova(cp->mdev, &iova, ccw->cda, sizeof(iova));
+		if (ret)
+			return ret;
+	} else {
+		iova = ccw->cda;
+	}
+	idaw_nr = idal_nr_words((void *)iova, bytes);
+	idal_len = idaw_nr * sizeof(*idaws);
+
+	/* Allocate an IDAL from host storage */
+	idaws = kcalloc(idaw_nr, sizeof(*idaws), GFP_DMA | GFP_KERNEL);
+	if (!idaws) {
+		ret = -ENOMEM;
+		goto out_init;
+	}
+
+	/*
+	 * Allocate an array of pfn's for pages to pin/translate.
+	 * The number of pages is actually the count of the idaws
+	 * required for the data transfer, since we only only support
+	 * 4K IDAWs today.
+	 */
+	pa = chain->ch_pa + idx;
+	ret = pfn_array_alloc(pa, iova, bytes);
+	if (ret < 0)
+		goto out_free_idaws;
+
+	if (ccw_is_idal(ccw)) {
+		/* Copy guest IDAL into host IDAL */
+		ret = copy_from_iova(cp->mdev, idaws, ccw->cda, idal_len);
+		if (ret)
+			goto out_unpin;
+
+		/*
+		 * Copy guest IDAWs into pfn_array, in case the memory they
+		 * occupy is not contiguous.
+		 */
+		for (i = 0; i < idaw_nr; i++)
+			pa->pa_iova_pfn[i] = idaws[i] >> PAGE_SHIFT;
+	} else {
+		/*
+		 * No action is required here; the iova addresses in pfn_array
+		 * were initialized sequentially in pfn_array_alloc() beginning
+		 * with the contents of ccw->cda.
+		 */
+	}
+
+	if (ccw_does_data_transfer(ccw)) {
+		ret = pfn_array_pin(pa, cp->mdev);
+		if (ret < 0)
+			goto out_unpin;
+	} else {
+		pa->pa_nr = 0;
+	}
+
+	ccw->cda = (__u32) virt_to_phys(idaws);
+	ccw->flags |= CCW_FLAG_IDA;
+
+	/* Populate the IDAL with pinned/translated addresses from pfn */
+	pfn_array_idal_create_words(pa, idaws);
+
+	return 0;
+
+out_unpin:
+	pfn_array_unpin_free(pa, cp->mdev);
+out_free_idaws:
+	kfree(idaws);
+out_init:
+	ccw->cda = 0;
+	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_tic(ccw))
+		return ccwchain_fetch_tic(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 idal(c64) ccw chaining.
+ * 2. 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)
+{
+	/* custom ratelimit used to avoid flood during guest IPL */
+	static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 1);
+	int ret;
+
+	/* this is an error in the caller */
+	if (cp->initialized)
+		return -EBUSY;
+
+	/*
+	 * We only support prefetching the channel program. We assume all channel
+	 * programs executed by supported guests likewise support prefetching.
+	 * Executing a channel program that does not specify prefetching will
+	 * typically not cause an error, but a warning is issued to help identify
+	 * the problem if something does break.
+	 */
+	if (!orb->cmd.pfch && __ratelimit(&ratelimit_state))
+		dev_warn(mdev, "Prefetching channel program even though prefetch not specified in ORB");
+
+	INIT_LIST_HEAD(&cp->ccwchain_list);
+	memcpy(&cp->orb, orb, sizeof(*orb));
+	cp->mdev = mdev;
+
+	/* Build a ccwchain for the first CCW segment */
+	ret = ccwchain_handle_ccw(orb->cmd.cpa, cp);
+
+	if (!ret) {
+		cp->initialized = true;
+
+		/* It is safe to force: if it was not set but idals used
+		 * ccwchain_calc_length would have returned an error.
+		 */
+		cp->orb.cmd.c64 = 1;
+	}
+
+	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)
+{
+	struct ccwchain *chain, *temp;
+	int i;
+
+	if (!cp->initialized)
+		return;
+
+	cp->initialized = false;
+	list_for_each_entry_safe(chain, temp, &cp->ccwchain_list, next) {
+		for (i = 0; i < chain->ch_len; i++) {
+			pfn_array_unpin_free(chain->ch_pa + i, cp->mdev);
+			ccwchain_cda_free(chain, i);
+		}
+		ccwchain_free(chain);
+	}
+}
+
+/**
+ * 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.
+ * For each chain composing the channel program:
+ * - On entry ch_len holds the count of CCWs to be translated.
+ * - On exit ch_len is adjusted to the count of successfully translated CCWs.
+ * This allows cp_free to find in ch_len the count of CCWs to free in a chain.
+ *
+ * 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;
+
+	/* this is an error in the caller */
+	if (!cp->initialized)
+		return -EINVAL;
+
+	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)
+				goto out_err;
+		}
+	}
+
+	return 0;
+out_err:
+	/* Only cleanup the chain elements that were actually translated. */
+	chain->ch_len = idx;
+	list_for_each_entry_continue(chain, &cp->ccwchain_list, next) {
+		chain->ch_len = 0;
+	}
+	return ret;
+}
+
+/**
+ * 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;
+
+	/* this is an error in the caller */
+	if (!cp->initialized)
+		return NULL;
+
+	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;
+
+	if (!cp->initialized)
+		return;
+
+	/*
+	 * 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;
+		/*
+		 * On successful execution, cpa points just beyond the end
+		 * of the chain.
+		 */
+		if (is_cpa_within_range(cpa, ccw_head, chain->ch_len + 1)) {
+			/*
+			 * (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.
+ * @cp: channel_program 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;
+
+	if (!cp->initialized)
+		return false;
+
+	list_for_each_entry(chain, &cp->ccwchain_list, next) {
+		for (i = 0; i < chain->ch_len; i++)
+			if (pfn_array_iova_pinned(chain->ch_pa + i, iova))
+				return true;
+	}
+
+	return false;
+}