Merge tag 'vfio-ccw-20190621' of https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/vfio-ccw into features

Refactoring of the vfio-ccw cp handling, simplifying the
code and avoiding unneeded allocating/copying.

* tag 'vfio-ccw-20190621' of https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/vfio-ccw:
  vfio-ccw: Remove copy_ccw_from_iova()
  vfio-ccw: Factor out the ccw0-to-ccw1 transition
  vfio-ccw: Copy CCW data outside length calculation
  vfio-ccw: Skip second copy of guest cp to host
  vfio-ccw: Move guest_cp storage into common struct
  s390/cio: Combine direct and indirect CCW paths
  vfio-ccw: Rearrange IDAL allocation in direct CCW
  vfio-ccw: Remove pfn_array_table
  vfio-ccw: Adjust the first IDAW outside of the nested loops
  vfio-ccw: Rearrange pfn_array and pfn_array_table arrays
  s390/cio: Use generalized CCW handler in cp_init()
  s390/cio: Generalize the TIC handler
  s390/cio: Refactor the routine that handles TIC CCWs
  s390/cio: Squash cp_free() and cp_unpin_free()

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

3 files changed, 151 insertions, 278 deletions

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index f73cfcfdd032..9cddc1288059 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -16,12 +16,6 @@
 
 #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 {
 	/* Starting guest physical I/O address. */
 	unsigned long		pa_iova;
@@ -33,11 +27,6 @@ struct pfn_array {
 	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;
@@ -46,7 +35,7 @@ struct ccwchain {
 	/* Count of the valid ccws in chain. */
 	int			ch_len;
 	/* Pinned PAGEs for the original data. */
-	struct pfn_array_table	*ch_pat;
+	struct pfn_array	*ch_pa;
 };
 
 /*
@@ -139,55 +128,23 @@ static void pfn_array_unpin_free(struct pfn_array *pa, struct device *mdev)
 	kfree(pa->pa_iova_pfn);
 }
 
-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)
+static bool pfn_array_iova_pinned(struct pfn_array *pa, unsigned long iova)
 {
-	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;
+	int i;
 
-	for (i = 0; i < pat->pat_nr; i++, pa++)
-		for (j = 0; j < pa->pa_nr; j++)
-			if (pa->pa_iova_pfn[j] == iova_pfn)
-				return true;
+	for (i = 0; i < pa->pa_nr; i++)
+		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,
+/* 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)
 {
-	struct pfn_array *pa;
-	int i, j, k;
+	int i;
 
 	/*
 	 * Idal words (execept the first one) rely on the memory being 4k
@@ -196,19 +153,36 @@ static inline void pfn_array_table_idal_create_words(
 	 * 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++;
+
+	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);
+}
+
+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).
@@ -254,40 +228,6 @@ static long copy_from_iova(struct device *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.
  */
@@ -377,7 +317,7 @@ static struct ccwchain *ccwchain_alloc(struct channel_program *cp, int len)
 	/* Make ccw address aligned to 8. */
 	size = ((sizeof(*chain) + 7L) & -8L) +
 		sizeof(*chain->ch_ccw) * len +
-		sizeof(*chain->ch_pat) * len;
+		sizeof(*chain->ch_pa) * len;
 	chain = kzalloc(size, GFP_DMA | GFP_KERNEL);
 	if (!chain)
 		return NULL;
@@ -386,7 +326,7 @@ static struct ccwchain *ccwchain_alloc(struct channel_program *cp, int len)
 	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_pa = (struct pfn_array *)data;
 
 	chain->ch_len = len;
 
@@ -412,23 +352,6 @@ static void ccwchain_cda_free(struct ccwchain *chain, int idx)
 	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;
-
-	cp->initialized = false;
-	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
@@ -444,25 +367,9 @@ static void cp_unpin_free(struct channel_program *cp)
  */
 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;
-	}
+	struct ccw1 *ccw = cp->guest_cp;
+	int cnt = 0;
 
-	cnt = 0;
 	do {
 		cnt++;
 
@@ -471,10 +378,8 @@ static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
 		 * 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)) {
-			kfree(p);
+		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
@@ -493,7 +398,6 @@ static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
 	if (cnt == CCWCHAIN_LEN_MAX + 1)
 		cnt = -EINVAL;
 
-	kfree(p);
 	return cnt;
 }
 
@@ -514,17 +418,23 @@ static int tic_target_chain_exists(struct ccw1 *tic, struct channel_program *cp)
 static int ccwchain_loop_tic(struct ccwchain *chain,
 			     struct channel_program *cp);
 
-static int ccwchain_handle_tic(struct ccw1 *tic, struct channel_program *cp)
+static int ccwchain_handle_ccw(u32 cda, struct channel_program *cp)
 {
 	struct ccwchain *chain;
-	int len, ret;
+	int len;
 
-	/* May transfer to an existing chain. */
-	if (tic_target_chain_exists(tic, cp))
-		return 0;
+	/* 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;
 
-	/* Get chain length. */
-	len = ccwchain_calc_length(tic->cda, cp);
+	/* Convert any Format-0 CCWs to Format-1 */
+	if (!cp->orb.cmd.fmt)
+		convert_ccw0_to_ccw1(cp->guest_cp, len);
+
+	/* Count the CCWs in the current chain */
+	len = ccwchain_calc_length(cda, cp);
 	if (len < 0)
 		return len;
 
@@ -532,14 +442,10 @@ static int ccwchain_handle_tic(struct ccw1 *tic, struct channel_program *cp)
 	chain = ccwchain_alloc(cp, len);
 	if (!chain)
 		return -ENOMEM;
-	chain->ch_iova = tic->cda;
+	chain->ch_iova = 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;
-	}
+	/* 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. */
 	return ccwchain_loop_tic(chain, cp);
@@ -557,7 +463,12 @@ static int ccwchain_loop_tic(struct ccwchain *chain, struct channel_program *cp)
 		if (!ccw_is_tic(tic))
 			continue;
 
-		ret = ccwchain_handle_tic(tic, cp);
+		/* 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;
 	}
@@ -590,131 +501,90 @@ static int ccwchain_fetch_direct(struct ccwchain *chain,
 				 struct channel_program *cp)
 {
 	struct ccw1 *ccw;
-	struct pfn_array_table *pat;
+	struct pfn_array *pa;
+	u64 iova;
 	unsigned long *idaws;
 	int ret;
 	int bytes = 1;
-	int idaw_nr = 1;
+	int idaw_nr, idal_len;
+	int i;
 
 	ccw = chain->ch_ccw + idx;
 
-	if (ccw->count) {
+	if (ccw->count)
 		bytes = ccw->count;
-		idaw_nr = idal_nr_words((void *)(u64)ccw->cda, ccw->count);
-	}
 
-	/*
-	 * 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;
-	ret = pfn_array_table_init(pat, 1);
-	if (ret)
-		goto out_init;
-
-	ret = pfn_array_alloc(pat->pat_pa, ccw->cda, bytes);
-	if (ret < 0)
-		goto out_unpin;
-
-	if (ccw_does_data_transfer(ccw)) {
-		ret = pfn_array_pin(pat->pat_pa, cp->mdev);
-		if (ret < 0)
-			goto out_unpin;
+	/* 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 {
-		pat->pat_pa->pa_nr = 0;
+		iova = ccw->cda;
 	}
+	idaw_nr = idal_nr_words((void *)iova, bytes);
+	idal_len = idaw_nr * sizeof(*idaws);
 
-	/* Translate this direct ccw to a idal ccw. */
+	/* Allocate an IDAL from host storage */
 	idaws = kcalloc(idaw_nr, sizeof(*idaws), GFP_DMA | GFP_KERNEL);
 	if (!idaws) {
 		ret = -ENOMEM;
-		goto out_unpin;
-	}
-	ccw->cda = (__u32) virt_to_phys(idaws);
-	ccw->flags |= CCW_FLAG_IDA;
-
-	pfn_array_table_idal_create_words(pat, idaws);
-
-	return 0;
-
-out_unpin:
-	pfn_array_table_unpin_free(pat, cp->mdev);
-out_init:
-	ccw->cda = 0;
-	return ret;
-}
-
-static int ccwchain_fetch_idal(struct ccwchain *chain,
-			       int idx,
-			       struct channel_program *cp)
-{
-	struct ccw1 *ccw;
-	struct pfn_array_table *pat;
-	struct pfn_array *pa;
-	unsigned long *idaws;
-	u64 idaw_iova;
-	unsigned int idaw_nr, idaw_len;
-	int i, ret;
-	int bytes = 1;
-
-	ccw = chain->ch_ccw + idx;
-
-	if (ccw->count)
-		bytes = ccw->count;
-
-	/* 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), bytes);
-	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)
 		goto out_init;
-
-	/* 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)
+	/*
+	 * 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;
 
-	ccw->cda = virt_to_phys(idaws);
-
-	for (i = 0; i < idaw_nr; i++) {
-		idaw_iova = *(idaws + i);
-		pa = pat->pat_pa + i;
-
-		ret = pfn_array_alloc(pa, idaw_iova, 1);
-		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;
 
-		if (!ccw_does_data_transfer(ccw)) {
-			pa->pa_nr = 0;
-			continue;
-		}
+		/*
+		 * 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_free_idaws;
+			goto out_unpin;
+	} else {
+		pa->pa_nr = 0;
 	}
 
-	pfn_array_table_idal_create_words(pat, idaws);
+	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_unpin:
-	pfn_array_table_unpin_free(pat, cp->mdev);
 out_init:
 	ccw->cda = 0;
 	return ret;
@@ -735,9 +605,6 @@ static int ccwchain_fetch_one(struct ccwchain *chain,
 	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);
 }
 
@@ -760,9 +627,7 @@ static int ccwchain_fetch_one(struct ccwchain *chain,
  */
 int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
 {
-	u64 iova = orb->cmd.cpa;
-	struct ccwchain *chain;
-	int len, ret;
+	int ret;
 
 	/*
 	 * XXX:
@@ -775,28 +640,11 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
 	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);
+	/* Build a ccwchain for the first CCW segment */
+	ret = ccwchain_handle_ccw(orb->cmd.cpa, cp);
 	if (ret)
-		cp_unpin_free(cp);
+		cp_free(cp);
+
 	/* It is safe to force: if not set but idals used
 	 * ccwchain_calc_length returns an error.
 	 */
@@ -819,8 +667,20 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
  */
 void cp_free(struct channel_program *cp)
 {
-	if (cp->initialized)
-		cp_unpin_free(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);
+	}
 }
 
 /**
@@ -992,8 +852,7 @@ bool cp_iova_pinned(struct channel_program *cp, u64 iova)
 
 	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))
+			if (pfn_array_iova_pinned(chain->ch_pa + i, iova))
 				return true;
 	}
 
diff --git a/drivers/s390/cio/vfio_ccw_cp.h b/drivers/s390/cio/vfio_ccw_cp.h
index 3c20cd208da5..7cdc38049033 100644
--- a/drivers/s390/cio/vfio_ccw_cp.h
+++ b/drivers/s390/cio/vfio_ccw_cp.h
@@ -16,6 +16,12 @@
 
 #include "orb.h"
 
+/*
+ * Max length for ccw chain.
+ * XXX: Limit to 256, need to check more?
+ */
+#define CCWCHAIN_LEN_MAX	256
+
 /**
  * struct channel_program - manage information for channel program
  * @ccwchain_list: list head of ccwchains
@@ -32,6 +38,7 @@ struct channel_program {
 	union orb orb;
 	struct device *mdev;
 	bool initialized;
+	struct ccw1 *guest_cp;
 };
 
 extern int cp_init(struct channel_program *cp, struct device *mdev,
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 66a66ac1f3d1..34a9a5e3fd36 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -129,6 +129,11 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
 	if (!private)
 		return -ENOMEM;
 
+	private->cp.guest_cp = kcalloc(CCWCHAIN_LEN_MAX, sizeof(struct ccw1),
+				       GFP_KERNEL);
+	if (!private->cp.guest_cp)
+		goto out_free;
+
 	private->io_region = kmem_cache_zalloc(vfio_ccw_io_region,
 					       GFP_KERNEL | GFP_DMA);
 	if (!private->io_region)
@@ -169,6 +174,7 @@ out_free:
 		kmem_cache_free(vfio_ccw_cmd_region, private->cmd_region);
 	if (private->io_region)
 		kmem_cache_free(vfio_ccw_io_region, private->io_region);
+	kfree(private->cp.guest_cp);
 	kfree(private);
 	return ret;
 }
@@ -185,6 +191,7 @@ static int vfio_ccw_sch_remove(struct subchannel *sch)
 
 	kmem_cache_free(vfio_ccw_cmd_region, private->cmd_region);
 	kmem_cache_free(vfio_ccw_io_region, private->io_region);
+	kfree(private->cp.guest_cp);
 	kfree(private);
 
 	return 0;