Merge remote-tracking branch 'kvms390/next'

7 files changed, 674 insertions, 6 deletions

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 4029943887a3..912b7df8215a 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3255,6 +3255,141 @@ Otherwise, if the MCE is a corrected error, KVM will just
 store it in the corresponding bank (provided this bank is
 not holding a previously reported uncorrected error).
 
+4.107 KVM_S390_GET_CMMA_BITS
+
+Capability: KVM_CAP_S390_CMMA_MIGRATION
+Architectures: s390
+Type: vm ioctl
+Parameters: struct kvm_s390_cmma_log (in, out)
+Returns: 0 on success, a negative value on error
+
+This ioctl is used to get the values of the CMMA bits on the s390
+architecture. It is meant to be used in two scenarios:
+- During live migration to save the CMMA values. Live migration needs
+  to be enabled via the KVM_REQ_START_MIGRATION VM property.
+- To non-destructively peek at the CMMA values, with the flag
+  KVM_S390_CMMA_PEEK set.
+
+The ioctl takes parameters via the kvm_s390_cmma_log struct. The desired
+values are written to a buffer whose location is indicated via the "values"
+member in the kvm_s390_cmma_log struct.  The values in the input struct are
+also updated as needed.
+Each CMMA value takes up one byte.
+
+struct kvm_s390_cmma_log {
+	__u64 start_gfn;
+	__u32 count;
+	__u32 flags;
+	union {
+		__u64 remaining;
+		__u64 mask;
+	};
+	__u64 values;
+};
+
+start_gfn is the number of the first guest frame whose CMMA values are
+to be retrieved,
+
+count is the length of the buffer in bytes,
+
+values points to the buffer where the result will be written to.
+
+If count is greater than KVM_S390_SKEYS_MAX, then it is considered to be
+KVM_S390_SKEYS_MAX. KVM_S390_SKEYS_MAX is re-used for consistency with
+other ioctls.
+
+The result is written in the buffer pointed to by the field values, and
+the values of the input parameter are updated as follows.
+
+Depending on the flags, different actions are performed. The only
+supported flag so far is KVM_S390_CMMA_PEEK.
+
+The default behaviour if KVM_S390_CMMA_PEEK is not set is:
+start_gfn will indicate the first page frame whose CMMA bits were dirty.
+It is not necessarily the same as the one passed as input, as clean pages
+are skipped.
+
+count will indicate the number of bytes actually written in the buffer.
+It can (and very often will) be smaller than the input value, since the
+buffer is only filled until 16 bytes of clean values are found (which
+are then not copied in the buffer). Since a CMMA migration block needs
+the base address and the length, for a total of 16 bytes, we will send
+back some clean data if there is some dirty data afterwards, as long as
+the size of the clean data does not exceed the size of the header. This
+allows to minimize the amount of data to be saved or transferred over
+the network at the expense of more roundtrips to userspace. The next
+invocation of the ioctl will skip over all the clean values, saving
+potentially more than just the 16 bytes we found.
+
+If KVM_S390_CMMA_PEEK is set:
+the existing storage attributes are read even when not in migration
+mode, and no other action is performed;
+
+the output start_gfn will be equal to the input start_gfn,
+
+the output count will be equal to the input count, except if the end of
+memory has been reached.
+
+In both cases:
+the field "remaining" will indicate the total number of dirty CMMA values
+still remaining, or 0 if KVM_S390_CMMA_PEEK is set and migration mode is
+not enabled.
+
+mask is unused.
+
+values points to the userspace buffer where the result will be stored.
+
+This ioctl can fail with -ENOMEM if not enough memory can be allocated to
+complete the task, with -ENXIO if CMMA is not enabled, with -EINVAL if
+KVM_S390_CMMA_PEEK is not set but migration mode was not enabled, with
+-EFAULT if the userspace address is invalid or if no page table is
+present for the addresses (e.g. when using hugepages).
+
+4.108 KVM_S390_SET_CMMA_BITS
+
+Capability: KVM_CAP_S390_CMMA_MIGRATION
+Architectures: s390
+Type: vm ioctl
+Parameters: struct kvm_s390_cmma_log (in)
+Returns: 0 on success, a negative value on error
+
+This ioctl is used to set the values of the CMMA bits on the s390
+architecture. It is meant to be used during live migration to restore
+the CMMA values, but there are no restrictions on its use.
+The ioctl takes parameters via the kvm_s390_cmma_values struct.
+Each CMMA value takes up one byte.
+
+struct kvm_s390_cmma_log {
+	__u64 start_gfn;
+	__u32 count;
+	__u32 flags;
+	union {
+		__u64 remaining;
+		__u64 mask;
+	};
+	__u64 values;
+};
+
+start_gfn indicates the starting guest frame number,
+
+count indicates how many values are to be considered in the buffer,
+
+flags is not used and must be 0.
+
+mask indicates which PGSTE bits are to be considered.
+
+remaining is not used.
+
+values points to the buffer in userspace where to store the values.
+
+This ioctl can fail with -ENOMEM if not enough memory can be allocated to
+complete the task, with -ENXIO if CMMA is not enabled, with -EINVAL if
+the count field is too large (e.g. more than KVM_S390_CMMA_SIZE_MAX) or
+if the flags field was not 0, with -EFAULT if the userspace address is
+invalid, if invalid pages are written to (e.g. after the end of memory)
+or if no page table is present for the addresses (e.g. when using
+hugepages).
+
 5. The kvm_run structure
 ------------------------
 
diff --git a/Documentation/virtual/kvm/devices/vm.txt b/Documentation/virtual/kvm/devices/vm.txt
index 575ccb022aac..903fc926860b 100644
--- a/Documentation/virtual/kvm/devices/vm.txt
+++ b/Documentation/virtual/kvm/devices/vm.txt
@@ -222,3 +222,36 @@ Allows user space to disable dea key wrapping, clearing the wrapping key.
 
 Parameters: none
 Returns:    0
+
+5. GROUP: KVM_S390_VM_MIGRATION
+Architectures: s390
+
+5.1. ATTRIBUTE: KVM_S390_VM_MIGRATION_STOP (w/o)
+
+Allows userspace to stop migration mode, needed for PGSTE migration.
+Setting this attribute when migration mode is not active will have no
+effects.
+
+Parameters: none
+Returns:    0
+
+5.2. ATTRIBUTE: KVM_S390_VM_MIGRATION_START (w/o)
+
+Allows userspace to start migration mode, needed for PGSTE migration.
+Setting this attribute when migration mode is already active will have
+no effects.
+
+Parameters: none
+Returns:    -ENOMEM if there is not enough free memory to start migration mode
+	    -EINVAL if the state of the VM is invalid (e.g. no memory defined)
+	    0 in case of success.
+
+5.3. ATTRIBUTE: KVM_S390_VM_MIGRATION_STATUS (r/o)
+
+Allows userspace to query the status of migration mode.
+
+Parameters: address of a buffer in user space to store the data (u64) to;
+	    the data itself is either 0 if migration mode is disabled or 1
+	    if it is enabled
+Returns:    -EFAULT if the given address is not accessible from kernel space
+	    0 in case of success.
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 426614a882a9..a8cafed79eb4 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -45,6 +45,8 @@
 #define KVM_REQ_ENABLE_IBS         8
 #define KVM_REQ_DISABLE_IBS        9
 #define KVM_REQ_ICPT_OPEREXC       10
+#define KVM_REQ_START_MIGRATION   11
+#define KVM_REQ_STOP_MIGRATION    12
 
 #define SIGP_CTRL_C		0x80
 #define SIGP_CTRL_SCN_MASK	0x3f
@@ -691,6 +693,12 @@ struct kvm_s390_vsie {
 	struct page *pages[KVM_MAX_VCPUS];
 };
 
+struct kvm_s390_migration_state {
+	unsigned long bitmap_size;	/* in bits (number of guest pages) */
+	atomic64_t dirty_pages;		/* number of dirty pages */
+	unsigned long *pgste_bitmap;
+};
+
 struct kvm_arch{
 	void *sca;
 	int use_esca;
@@ -718,6 +726,7 @@ struct kvm_arch{
 	struct kvm_s390_crypto crypto;
 	struct kvm_s390_vsie vsie;
 	u64 epoch;
+	struct kvm_s390_migration_state *migration_state;
 	/* subset of available cpu features enabled by user space */
 	DECLARE_BITMAP(cpu_feat, KVM_S390_VM_CPU_FEAT_NR_BITS);
 };
diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 3dd2a1d308dd..d6879a916de5 100644
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -70,6 +70,7 @@ struct kvm_s390_io_adapter_req {
 #define KVM_S390_VM_TOD			1
 #define KVM_S390_VM_CRYPTO		2
 #define KVM_S390_VM_CPU_MODEL		3
+#define KVM_S390_VM_MIGRATION		4
 
 /* kvm attributes for mem_ctrl */
 #define KVM_S390_VM_MEM_ENABLE_CMMA	0
@@ -151,6 +152,11 @@ struct kvm_s390_vm_cpu_subfunc {
 #define KVM_S390_VM_CRYPTO_DISABLE_AES_KW	2
 #define KVM_S390_VM_CRYPTO_DISABLE_DEA_KW	3
 
+/* kvm attributes for migration mode */
+#define KVM_S390_VM_MIGRATION_STOP	0
+#define KVM_S390_VM_MIGRATION_START	1
+#define KVM_S390_VM_MIGRATION_STATUS	2
+
 /* for KVM_GET_REGS and KVM_SET_REGS */
 struct kvm_regs {
 	/* general purpose regs for s390 */
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 689ac48361c6..4ef3035d4dc4 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -30,6 +30,7 @@
 #include <linux/vmalloc.h>
 #include <linux/bitmap.h>
 #include <linux/sched/signal.h>
+#include <linux/string.h>
 
 #include <asm/asm-offsets.h>
 #include <asm/lowcore.h>
@@ -386,6 +387,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_S390_SKEYS:
 	case KVM_CAP_S390_IRQ_STATE:
 	case KVM_CAP_S390_USER_INSTR0:
+	case KVM_CAP_S390_CMMA_MIGRATION:
 	case KVM_CAP_S390_AIS:
 		r = 1;
 		break;
@@ -750,6 +752,131 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr)
 	return 0;
 }
 
+static void kvm_s390_sync_request_broadcast(struct kvm *kvm, int req)
+{
+	int cx;
+	struct kvm_vcpu *vcpu;
+
+	kvm_for_each_vcpu(cx, vcpu, kvm)
+		kvm_s390_sync_request(req, vcpu);
+}
+
+/*
+ * Must be called with kvm->srcu held to avoid races on memslots, and with
+ * kvm->lock to avoid races with ourselves and kvm_s390_vm_stop_migration.
+ */
+static int kvm_s390_vm_start_migration(struct kvm *kvm)
+{
+	struct kvm_s390_migration_state *mgs;
+	struct kvm_memory_slot *ms;
+	/* should be the only one */
+	struct kvm_memslots *slots;
+	unsigned long ram_pages;
+	int slotnr;
+
+	/* migration mode already enabled */
+	if (kvm->arch.migration_state)
+		return 0;
+
+	slots = kvm_memslots(kvm);
+	if (!slots)
+		return -EINVAL;
+	if (!slots->used_slots)
+		return -EINVAL;
+
+	mgs = kzalloc(sizeof(*mgs), GFP_KERNEL);
+	if (!mgs)
+		return -ENOMEM;
+	kvm->arch.migration_state = mgs;
+
+	if (kvm->arch.use_cmma && slots) {
+		/*
+		 * Get the last slot. They should be sorted by base_gfn, so the
+		 * last slot is also the one at the end of the address space.
+		 * We have verified above that at least one slot is present.
+		 */
+		ms = slots->memslots + slots->used_slots - 1;
+		/* round up so we only use full longs */
+		ram_pages = roundup(ms->base_gfn + ms->npages, BITS_PER_LONG);
+		/* allocate enough bytes to store all the bits */
+		mgs->pgste_bitmap = vmalloc(ram_pages / 8);
+		if (!mgs->pgste_bitmap) {
+			kfree(mgs);
+			kvm->arch.migration_state = NULL;
+			return -ENOMEM;
+		}
+
+		mgs->bitmap_size = ram_pages;
+		atomic64_set(&mgs->dirty_pages, ram_pages);
+		/* mark all the pages in active slots as dirty */
+		for (slotnr = 0; slotnr < slots->used_slots; slotnr++) {
+			ms = slots->memslots + slotnr;
+			bitmap_set(mgs->pgste_bitmap, ms->base_gfn, ms->npages);
+		}
+
+		kvm_s390_sync_request_broadcast(kvm, KVM_REQ_START_MIGRATION);
+	}
+	return 0;
+}
+
+/*
+ * Must be called with kvm->lock to avoid races with ourselves and
+ * kvm_s390_vm_start_migration.
+ */
+static int kvm_s390_vm_stop_migration(struct kvm *kvm)
+{
+	struct kvm_s390_migration_state *mgs;
+
+	/* migration mode already disabled */
+	if (!kvm->arch.migration_state)
+		return 0;
+	mgs = kvm->arch.migration_state;
+	kvm->arch.migration_state = NULL;
+
+	if (kvm->arch.use_cmma) {
+		kvm_s390_sync_request_broadcast(kvm, KVM_REQ_STOP_MIGRATION);
+		vfree(mgs->pgste_bitmap);
+	}
+	kfree(mgs);
+	return 0;
+}
+
+static int kvm_s390_vm_set_migration(struct kvm *kvm,
+				     struct kvm_device_attr *attr)
+{
+	int idx, res = -ENXIO;
+
+	mutex_lock(&kvm->lock);
+	switch (attr->attr) {
+	case KVM_S390_VM_MIGRATION_START:
+		idx = srcu_read_lock(&kvm->srcu);
+		res = kvm_s390_vm_start_migration(kvm);
+		srcu_read_unlock(&kvm->srcu, idx);
+		break;
+	case KVM_S390_VM_MIGRATION_STOP:
+		res = kvm_s390_vm_stop_migration(kvm);
+		break;
+	default:
+		break;
+	}
+	mutex_unlock(&kvm->lock);
+
+	return res;
+}
+
+static int kvm_s390_vm_get_migration(struct kvm *kvm,
+				     struct kvm_device_attr *attr)
+{
+	u64 mig = (kvm->arch.migration_state != NULL);
+
+	if (attr->attr != KVM_S390_VM_MIGRATION_STATUS)
+		return -ENXIO;
+
+	if (copy_to_user((void __user *)attr->addr, &mig, sizeof(mig)))
+		return -EFAULT;
+	return 0;
+}
+
 static int kvm_s390_set_tod_high(struct kvm *kvm, struct kvm_device_attr *attr)
 {
 	u8 gtod_high;
@@ -1090,6 +1217,9 @@ static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 	case KVM_S390_VM_CRYPTO:
 		ret = kvm_s390_vm_set_crypto(kvm, attr);
 		break;
+	case KVM_S390_VM_MIGRATION:
+		ret = kvm_s390_vm_set_migration(kvm, attr);
+		break;
 	default:
 		ret = -ENXIO;
 		break;
@@ -1112,6 +1242,9 @@ static int kvm_s390_vm_get_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 	case KVM_S390_VM_CPU_MODEL:
 		ret = kvm_s390_get_cpu_model(kvm, attr);
 		break;
+	case KVM_S390_VM_MIGRATION:
+		ret = kvm_s390_vm_get_migration(kvm, attr);
+		break;
 	default:
 		ret = -ENXIO;
 		break;
@@ -1179,6 +1312,9 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 			break;
 		}
 		break;
+	case KVM_S390_VM_MIGRATION:
+		ret = 0;
+		break;
 	default:
 		ret = -ENXIO;
 		break;
@@ -1286,6 +1422,182 @@ out:
 	return r;
 }
 
+/*
+ * Base address and length must be sent at the start of each block, therefore
+ * it's cheaper to send some clean data, as long as it's less than the size of
+ * two longs.
+ */
+#define KVM_S390_MAX_BIT_DISTANCE (2 * sizeof(void *))
+/* for consistency */
+#define KVM_S390_CMMA_SIZE_MAX ((u32)KVM_S390_SKEYS_MAX)
+
+/*
+ * This function searches for the next page with dirty CMMA attributes, and
+ * saves the attributes in the buffer up to either the end of the buffer or
+ * until a block of at least KVM_S390_MAX_BIT_DISTANCE clean bits is found;
+ * no trailing clean bytes are saved.
+ * In case no dirty bits were found, or if CMMA was not enabled or used, the
+ * output buffer will indicate 0 as length.
+ */
+static int kvm_s390_get_cmma_bits(struct kvm *kvm,
+				  struct kvm_s390_cmma_log *args)
+{
+	struct kvm_s390_migration_state *s = kvm->arch.migration_state;
+	unsigned long bufsize, hva, pgstev, i, next, cur;
+	int srcu_idx, peek, r = 0, rr;
+	u8 *res;
+
+	cur = args->start_gfn;
+	i = next = pgstev = 0;
+
+	if (unlikely(!kvm->arch.use_cmma))
+		return -ENXIO;
+	/* Invalid/unsupported flags were specified */
+	if (args->flags & ~KVM_S390_CMMA_PEEK)
+		return -EINVAL;
+	/* Migration mode query, and we are not doing a migration */
+	peek = !!(args->flags & KVM_S390_CMMA_PEEK);
+	if (!peek && !s)
+		return -EINVAL;
+	/* CMMA is disabled or was not used, or the buffer has length zero */
+	bufsize = min(args->count, KVM_S390_CMMA_SIZE_MAX);
+	if (!bufsize || !kvm->mm->context.use_cmma) {
+		memset(args, 0, sizeof(*args));
+		return 0;
+	}
+
+	if (!peek) {
+		/* We are not peeking, and there are no dirty pages */
+		if (!atomic64_read(&s->dirty_pages)) {
+			memset(args, 0, sizeof(*args));
+			return 0;
+		}
+		cur = find_next_bit(s->pgste_bitmap, s->bitmap_size,
+					args->start_gfn);
+		if (cur >= s->bitmap_size)	/* nothing found, loop back */
+			cur = find_next_bit(s->pgste_bitmap, s->bitmap_size, 0);
+		if (cur >= s->bitmap_size) {	/* again! (very unlikely) */
+			memset(args, 0, sizeof(*args));
+			return 0;
+		}
+		next = find_next_bit(s->pgste_bitmap, s->bitmap_size, cur + 1);
+	}
+
+	res = vmalloc(bufsize);
+	if (!res)
+		return -ENOMEM;
+
+	args->start_gfn = cur;
+
+	down_read(&kvm->mm->mmap_sem);
+	srcu_idx = srcu_read_lock(&kvm->srcu);
+	while (i < bufsize) {
+		hva = gfn_to_hva(kvm, cur);
+		if (kvm_is_error_hva(hva)) {
+			r = -EFAULT;
+			break;
+		}
+		/* decrement only if we actually flipped the bit to 0 */
+		if (!peek && test_and_clear_bit(cur, s->pgste_bitmap))
+			atomic64_dec(&s->dirty_pages);
+		r = get_pgste(kvm->mm, hva, &pgstev);
+		if (r < 0)
+			pgstev = 0;
+		/* save the value */
+		res[i++] = (pgstev >> 24) & 0x3;
+		/*
+		 * if the next bit is too far away, stop.
+		 * if we reached the previous "next", find the next one
+		 */
+		if (!peek) {
+			if (next > cur + KVM_S390_MAX_BIT_DISTANCE)
+				break;
+			if (cur == next)
+				next = find_next_bit(s->pgste_bitmap,
+						s->bitmap_size, cur + 1);
+		/* reached the end of the bitmap or of the buffer, stop */
+			if ((next >= s->bitmap_size) ||
+				(next >= args->start_gfn + bufsize))
+				break;
+		}
+		cur++;
+	}
+	srcu_read_unlock(&kvm->srcu, srcu_idx);
+	up_read(&kvm->mm->mmap_sem);
+	args->count = i;
+	args->remaining = s ? atomic64_read(&s->dirty_pages) : 0;
+
+	rr = copy_to_user((void __user *)args->values, res, args->count);
+	if (rr)
+		r = -EFAULT;
+
+	vfree(res);
+	return r;
+}
+
+/*
+ * This function sets the CMMA attributes for the given pages. If the input
+ * buffer has zero length, no action is taken, otherwise the attributes are
+ * set and the mm->context.use_cmma flag is set.
+ */
+static int kvm_s390_set_cmma_bits(struct kvm *kvm,
+				  const struct kvm_s390_cmma_log *args)
+{
+	unsigned long hva, mask, pgstev, i;
+	uint8_t *bits;
+	int srcu_idx, r = 0;
+
+	mask = args->mask;
+
+	if (!kvm->arch.use_cmma)
+		return -ENXIO;
+	/* invalid/unsupported flags */
+	if (args->flags != 0)
+		return -EINVAL;
+	/* Enforce sane limit on memory allocation */
+	if (args->count > KVM_S390_CMMA_SIZE_MAX)
+		return -EINVAL;
+	/* Nothing to do */
+	if (args->count == 0)
+		return 0;
+
+	bits = vmalloc(sizeof(*bits) * args->count);
+	if (!bits)
+		return -ENOMEM;
+
+	r = copy_from_user(bits, (void __user *)args->values, args->count);
+	if (r) {
+		r = -EFAULT;
+		goto out;
+	}
+
+	down_read(&kvm->mm->mmap_sem);
+	srcu_idx = srcu_read_lock(&kvm->srcu);
+	for (i = 0; i < args->count; i++) {
+		hva = gfn_to_hva(kvm, args->start_gfn + i);
+		if (kvm_is_error_hva(hva)) {
+			r = -EFAULT;
+			break;
+		}
+
+		pgstev = bits[i];
+		pgstev = pgstev << 24;
+		mask &= _PGSTE_GPS_USAGE_MASK;
+		set_pgste_bits(kvm->mm, hva, mask, pgstev);
+	}
+	srcu_read_unlock(&kvm->srcu, srcu_idx);
+	up_read(&kvm->mm->mmap_sem);
+
+	if (!kvm->mm->context.use_cmma) {
+		down_write(&kvm->mm->mmap_sem);
+		kvm->mm->context.use_cmma = 1;
+		up_write(&kvm->mm->mmap_sem);
+	}
+out:
+	vfree(bits);
+	return r;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -1364,6 +1676,29 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		r = kvm_s390_set_skeys(kvm, &args);
 		break;
 	}
+	case KVM_S390_GET_CMMA_BITS: {
+		struct kvm_s390_cmma_log args;
+
+		r = -EFAULT;
+		if (copy_from_user(&args, argp, sizeof(args)))
+			break;
+		r = kvm_s390_get_cmma_bits(kvm, &args);
+		if (!r) {
+			r = copy_to_user(argp, &args, sizeof(args));
+			if (r)
+				r = -EFAULT;
+		}
+		break;
+	}
+	case KVM_S390_SET_CMMA_BITS: {
+		struct kvm_s390_cmma_log args;
+
+		r = -EFAULT;
+		if (copy_from_user(&args, argp, sizeof(args)))
+			break;
+		r = kvm_s390_set_cmma_bits(kvm, &args);
+		break;
+	}
 	default:
 		r = -ENOTTY;
 	}
@@ -1633,6 +1968,10 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
 	kvm_s390_destroy_adapters(kvm);
 	kvm_s390_clear_float_irqs(kvm);
 	kvm_s390_vsie_destroy(kvm);
+	if (kvm->arch.migration_state) {
+		vfree(kvm->arch.migration_state->pgste_bitmap);
+		kfree(kvm->arch.migration_state);
+	}
 	KVM_EVENT(3, "vm 0x%pK destroyed", kvm);
 }
 
@@ -1977,7 +2316,6 @@ int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu)
 	if (!vcpu->arch.sie_block->cbrlo)
 		return -ENOMEM;
 
-	vcpu->arch.sie_block->ecb2 |= ECB2_CMMA;
 	vcpu->arch.sie_block->ecb2 &= ~ECB2_PFMFI;
 	return 0;
 }
@@ -2489,6 +2827,27 @@ retry:
 		goto retry;
 	}
 
+	if (kvm_check_request(KVM_REQ_START_MIGRATION, vcpu)) {
+		/*
+		 * Disable CMMA virtualization; we will emulate the ESSA
+		 * instruction manually, in order to provide additional
+		 * functionalities needed for live migration.
+		 */
+		vcpu->arch.sie_block->ecb2 &= ~ECB2_CMMA;
+		goto retry;
+	}
+
+	if (kvm_check_request(KVM_REQ_STOP_MIGRATION, vcpu)) {
+		/*
+		 * Re-enable CMMA virtualization if CMMA is available and
+		 * was used.
+		 */
+		if ((vcpu->kvm->arch.use_cmma) &&
+					(vcpu->kvm->mm->context.use_cmma))
+			vcpu->arch.sie_block->ecb2 |= ECB2_CMMA;
+		goto retry;
+	}
+
 	/* nothing to do, just clear the request */
 	kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index c03106c428cf..a226c459809b 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -24,6 +24,7 @@
 #include <asm/ebcdic.h>
 #include <asm/sysinfo.h>
 #include <asm/pgtable.h>
+#include <asm/page-states.h>
 #include <asm/pgalloc.h>
 #include <asm/gmap.h>
 #include <asm/io.h>
@@ -949,13 +950,72 @@ static int handle_pfmf(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
+static inline int do_essa(struct kvm_vcpu *vcpu, const int orc)
+{
+	struct kvm_s390_migration_state *ms = vcpu->kvm->arch.migration_state;
+	int r1, r2, nappended, entries;
+	unsigned long gfn, hva, res, pgstev, ptev;
+	unsigned long *cbrlo;
+
+	/*
+	 * We don't need to set SD.FPF.SK to 1 here, because if we have a
+	 * machine check here we either handle it or crash
+	 */
+
+	kvm_s390_get_regs_rre(vcpu, &r1, &r2);
+	gfn = vcpu->run->s.regs.gprs[r2] >> PAGE_SHIFT;
+	hva = gfn_to_hva(vcpu->kvm, gfn);
+	entries = (vcpu->arch.sie_block->cbrlo & ~PAGE_MASK) >> 3;
+
+	if (kvm_is_error_hva(hva))
+		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
+
+	nappended = pgste_perform_essa(vcpu->kvm->mm, hva, orc, &ptev, &pgstev);
+	if (nappended < 0) {
+		res = orc ? 0x10 : 0;
+		vcpu->run->s.regs.gprs[r1] = res; /* Exception Indication */
+		return 0;
+	}
+	res = (pgstev & _PGSTE_GPS_USAGE_MASK) >> 22;
+	/*
+	 * Set the block-content state part of the result. 0 means resident, so
+	 * nothing to do if the page is valid. 2 is for preserved pages
+	 * (non-present and non-zero), and 3 for zero pages (non-present and
+	 * zero).
+	 */
+	if (ptev & _PAGE_INVALID) {
+		res |= 2;
+		if (pgstev & _PGSTE_GPS_ZERO)
+			res |= 1;
+	}
+	vcpu->run->s.regs.gprs[r1] = res;
+	/*
+	 * It is possible that all the normal 511 slots were full, in which case
+	 * we will now write in the 512th slot, which is reserved for host use.
+	 * In both cases we let the normal essa handling code process all the
+	 * slots, including the reserved one, if needed.
+	 */
+	if (nappended > 0) {
+		cbrlo = phys_to_virt(vcpu->arch.sie_block->cbrlo & PAGE_MASK);
+		cbrlo[entries] = gfn << PAGE_SHIFT;
+	}
+
+	if (orc) {
+		/* increment only if we are really flipping the bit to 1 */
+		if (!test_and_set_bit(gfn, ms->pgste_bitmap))
+			atomic64_inc(&ms->dirty_pages);
+	}
+
+	return nappended;
+}
+
 static int handle_essa(struct kvm_vcpu *vcpu)
 {
 	/* entries expected to be 1FF */
 	int entries = (vcpu->arch.sie_block->cbrlo & ~PAGE_MASK) >> 3;
 	unsigned long *cbrlo;
 	struct gmap *gmap;
-	int i;
+	int i, orc;
 
 	VCPU_EVENT(vcpu, 4, "ESSA: release %d pages", entries);
 	gmap = vcpu->arch.gmap;
@@ -965,12 +1025,45 @@ static int handle_essa(struct kvm_vcpu *vcpu)
 
 	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
 		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
-
-	if (((vcpu->arch.sie_block->ipb & 0xf0000000) >> 28) > 6)
+	/* Check for invalid operation request code */
+	orc = (vcpu->arch.sie_block->ipb & 0xf0000000) >> 28;
+	if (orc > ESSA_MAX)
 		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
 
-	/* Retry the ESSA instruction */
-	kvm_s390_retry_instr(vcpu);
+	if (likely(!vcpu->kvm->arch.migration_state)) {
+		/*
+		 * CMMA is enabled in the KVM settings, but is disabled in
+		 * the SIE block and in the mm_context, and we are not doing
+		 * a migration. Enable CMMA in the mm_context.
+		 * Since we need to take a write lock to write to the context
+		 * to avoid races with storage keys handling, we check if the
+		 * value really needs to be written to; if the value is
+		 * already correct, we do nothing and avoid the lock.
+		 */
+		if (vcpu->kvm->mm->context.use_cmma == 0) {
+			down_write(&vcpu->kvm->mm->mmap_sem);
+			vcpu->kvm->mm->context.use_cmma = 1;
+			up_write(&vcpu->kvm->mm->mmap_sem);
+		}
+		/*
+		 * If we are here, we are supposed to have CMMA enabled in
+		 * the SIE block. Enabling CMMA works on a per-CPU basis,
+		 * while the context use_cmma flag is per process.
+		 * It's possible that the context flag is enabled and the
+		 * SIE flag is not, so we set the flag always; if it was
+		 * already set, nothing changes, otherwise we enable it
+		 * on this CPU too.
+		 */
+		vcpu->arch.sie_block->ecb2 |= ECB2_CMMA;
+		/* Retry the ESSA instruction */
+		kvm_s390_retry_instr(vcpu);
+	} else {
+		/* Account for the possible extra cbrl entry */
+		i = do_essa(vcpu, orc);
+		if (i < 0)
+			return i;
+		entries += i;
+	}
 	vcpu->arch.sie_block->cbrlo &= PAGE_MASK;	/* reset nceo */
 	cbrlo = phys_to_virt(vcpu->arch.sie_block->cbrlo);
 	down_read(&gmap->mm->mmap_sem);
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 577429a95ad8..2b8dc1ca18d4 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -155,6 +155,35 @@ struct kvm_s390_skeys {
 	__u32 reserved[9];
 };
 
+#define KVM_S390_CMMA_PEEK (1 << 0)
+
+/**
+ * kvm_s390_cmma_log - Used for CMMA migration.
+ *
+ * Used both for input and output.
+ *
+ * @start_gfn: Guest page number to start from.
+ * @count: Size of the result buffer.
+ * @flags: Control operation mode via KVM_S390_CMMA_* flags
+ * @remaining: Used with KVM_S390_GET_CMMA_BITS. Indicates how many dirty
+ *             pages are still remaining.
+ * @mask: Used with KVM_S390_SET_CMMA_BITS. Bitmap of bits to actually set
+ *        in the PGSTE.
+ * @values: Pointer to the values buffer.
+ *
+ * Used in KVM_S390_{G,S}ET_CMMA_BITS ioctls.
+ */
+struct kvm_s390_cmma_log {
+	__u64 start_gfn;
+	__u32 count;
+	__u32 flags;
+	union {
+		__u64 remaining;
+		__u64 mask;
+	};
+	__u64 values;
+};
+
 struct kvm_hyperv_exit {
 #define KVM_EXIT_HYPERV_SYNIC          1
 #define KVM_EXIT_HYPERV_HCALL          2
@@ -895,6 +924,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_SPAPR_TCE_VFIO 142
 #define KVM_CAP_X86_GUEST_MWAIT 143
 #define KVM_CAP_ARM_USER_IRQ 144
+#define KVM_CAP_S390_CMMA_MIGRATION 145
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1318,6 +1348,9 @@ struct kvm_s390_ucas_mapping {
 #define KVM_S390_GET_IRQ_STATE	  _IOW(KVMIO, 0xb6, struct kvm_s390_irq_state)
 /* Available with KVM_CAP_X86_SMM */
 #define KVM_SMI                   _IO(KVMIO,   0xb7)
+/* Available with KVM_CAP_S390_CMMA_MIGRATION */
+#define KVM_S390_GET_CMMA_BITS      _IOW(KVMIO, 0xb8, struct kvm_s390_cmma_log)
+#define KVM_S390_SET_CMMA_BITS      _IOW(KVMIO, 0xb9, struct kvm_s390_cmma_log)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)