This is a fix for several issues that were found in the original code
for storage attributes migration.
Now no bitmap is allocated to keep track of dirty storage attributes;
the extra bits of the per-memslot bitmap that are always present anyway
are now used for this purpose.
The code has also been refactored a little to improve readability.
Fixes: 190df4a212a ("KVM: s390: CMMA tracking, ESSA emulation, migration mode")
Fixes: 4036e3874a1 ("KVM: s390: ioctls to get and set guest storage attributes")
Acked-by: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxxxxxxx>
---
arch/s390/include/asm/kvm_host.h | 9 +-
arch/s390/kvm/kvm-s390.c | 293 +++++++++++++++++++++++----------------
arch/s390/kvm/priv.c | 28 ++--
3 files changed, 195 insertions(+), 135 deletions(-)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index c1b0a9a..0362706 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -725,12 +725,6 @@ 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;
@@ -758,7 +752,8 @@ struct kvm_arch{
struct kvm_s390_vsie vsie;
u8 epdx;
u64 epoch;
- struct kvm_s390_migration_state *migration_state;
+ int migration_mode;
+ atomic64_t cmma_dirty_pages;
/* 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/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 1371dff..614aa43 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -773,54 +773,37 @@ static void kvm_s390_sync_request_broadcast(struct kvm *kvm, int req)
*/
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;
+ unsigned long ram_pages = 0;
int slotnr;
/* migration mode already enabled */
- if (kvm->arch.migration_state)
+ if (kvm->arch.migration_mode)
return 0;
-
slots = kvm_memslots(kvm);
if (!slots || !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) {
+ if (!kvm->arch.use_cmma) {
+ kvm->arch.migration_mode = 1;
+ return 0;
+ }
+ /* mark all the pages in active slots as dirty */
+ for (slotnr = 0; slotnr < slots->used_slots; slotnr++) {
+ ms = slots->memslots + slotnr;
/*
- * Get the first slot. They are reverse sorted by base_gfn, so
- * the first slot is also the one at the end of the address
- * space. We have verified above that at least one slot is
- * present.
+ * The second half of the bitmap is only used on x86,
+ * and would be wasted otherwise, so we put it to good
+ * use here to keep track of the state of the storage
+ * attributes.
*/
- ms = slots->memslots;
- /* 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);
+ memset(kvm_second_dirty_bitmap(ms), 0xff, kvm_dirty_bitmap_bytes(ms));
+ ram_pages += ms->npages;
}
+ atomic64_set(&kvm->arch.cmma_dirty_pages, ram_pages);
+ kvm->arch.migration_mode = 1;
+ kvm_s390_sync_request_broadcast(kvm, KVM_REQ_START_MIGRATION);
return 0;
}
@@ -830,21 +813,12 @@ static int kvm_s390_vm_start_migration(struct kvm *kvm)
*/
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)
+ if (!kvm->arch.migration_mode)
return 0;
- mgs = kvm->arch.migration_state;
- kvm->arch.migration_state = NULL;
-
- if (kvm->arch.use_cmma) {
+ kvm->arch.migration_mode = 0;
+ if (kvm->arch.use_cmma)
kvm_s390_sync_request_broadcast(kvm, KVM_REQ_STOP_MIGRATION);
- /* We have to wait for the essa emulation to finish */
- synchronize_srcu(&kvm->srcu);
- vfree(mgs->pgste_bitmap);
- }
- kfree(mgs);
return 0;
}
@@ -872,7 +846,7 @@ static int kvm_s390_vm_set_migration(struct kvm *kvm,
static int kvm_s390_vm_get_migration(struct kvm *kvm,
struct kvm_device_attr *attr)
{
- u64 mig = (kvm->arch.migration_state != NULL);
+ u64 mig = kvm->arch.migration_mode;
if (attr->attr != KVM_S390_VM_MIGRATION_STATUS)
return -ENXIO;
@@ -1504,6 +1478,134 @@ static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
#define KVM_S390_CMMA_SIZE_MAX ((u32)KVM_S390_SKEYS_MAX)
/*
+ * Similar to gfn_to_memslot, but returns the index of a memslot also when the
+ * address falls in a hole. In that case the index of one of the memslots
+ * bordering the hole is returned.
+ */
+static int gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn)
+{
+ int start = 0, end = slots->used_slots;
+ int slot = atomic_read(&slots->lru_slot);
+ struct kvm_memory_slot *memslots = slots->memslots;
+
+ if (gfn >= memslots[slot].base_gfn &&
+ gfn < memslots[slot].base_gfn + memslots[slot].npages)
+ return slot;
+
+ while (start < end) {
+ slot = start + (end - start) / 2;
+
+ if (gfn >= memslots[slot].base_gfn)
+ end = slot;
+ else
+ start = slot + 1;
+ }
+
+ if (gfn >= memslots[start].base_gfn &&
+ gfn < memslots[start].base_gfn + memslots[start].npages) {
+ atomic_set(&slots->lru_slot, start);
+ }
+
+ return start;
+}
+
+static int kvm_s390_peek_cmma(struct kvm *kvm, struct kvm_s390_cmma_log *args,
+ u8 *res, unsigned long bufsize)
+{
+ unsigned long pgstev, hva, cur_gfn = args->start_gfn;
+
+ args->count = 0;
+ while (args->count < bufsize) {
+ hva = gfn_to_hva(kvm, cur_gfn);
+ /*
+ * We return an error if the first value was invalid, but we
+ * return successfully if at least one value was copied.
+ */
+ if (kvm_is_error_hva(hva))
+ return args->count ? 0 : -EFAULT;
+ if (get_pgste(kvm->mm, hva, &pgstev) < 0)
+ pgstev = 0;
+ res[args->count++] = (pgstev >> 24) & 0x43;
+ cur_gfn++;
+ }
+
+ return 0;
+}
+
+static unsigned long kvm_s390_next_dirty_cmma(struct kvm_memslots *slots,
+ unsigned long cur_gfn)
+{
+ int slotidx = gfn_to_memslot_approx(slots, cur_gfn);
+ struct kvm_memory_slot *ms = slots->memslots + slotidx;
+ unsigned long ofs = cur_gfn - ms->base_gfn;
+
+ if (ms->base_gfn + ms->npages <= cur_gfn) {
+ slotidx--;
+ /* If we are above the highest slot, wrap around */
+ if (slotidx < 0)
+ slotidx = slots->used_slots - 1;
+
+ ms = slots->memslots + slotidx;
+ ofs = 0;
+ }
+ ofs = find_next_bit(kvm_second_dirty_bitmap(ms), ms->npages, ofs);
+ while ((slotidx > 0) && (ofs >= ms->npages)) {
+ slotidx--;
+ ms = slots->memslots + slotidx;
+ ofs = find_next_bit(kvm_second_dirty_bitmap(ms), ms->npages, 0);
+ }
+ return ms->base_gfn + ofs;
+}
+
+static int kvm_s390_get_cmma(struct kvm *kvm, struct kvm_s390_cmma_log *args,
+ u8 *res, unsigned long bufsize)
+{
+ unsigned long mem_end, cur_gfn, next_gfn, hva, pgstev;
+ struct kvm_memslots *slots = kvm_memslots(kvm);
+ struct kvm_memory_slot *ms;
+
+ cur_gfn = kvm_s390_next_dirty_cmma(slots, args->start_gfn);
+ ms = gfn_to_memslot(kvm, cur_gfn);
+ args->count = 0;
+ args->start_gfn = cur_gfn;
+ if (!ms)
+ return 0;
+ next_gfn = kvm_s390_next_dirty_cmma(slots, cur_gfn + 1);
+ mem_end = slots->memslots[0].base_gfn + slots->memslots[0].npages;
+
+ while (args->count < bufsize) {
+ hva = gfn_to_hva(kvm, cur_gfn);
+ if (kvm_is_error_hva(hva))
+ return 0;
+ /* Decrement only if we actually flipped the bit to 0 */
+ if (test_and_clear_bit(cur_gfn - ms->base_gfn, kvm_second_dirty_bitmap(ms)))
+ atomic64_dec(&kvm->arch.cmma_dirty_pages);
+ if (get_pgste(kvm->mm, hva, &pgstev) < 0)
+ pgstev = 0;
+ /* Save the value */
+ res[args->count++] = (pgstev >> 24) & 0x43;
+ /* If the next bit is too far away, stop. */
+ if (next_gfn > cur_gfn + KVM_S390_MAX_BIT_DISTANCE)
+ return 0;
+ /* If we reached the previous "next", find the next one */
+ if (cur_gfn == next_gfn)
+ next_gfn = kvm_s390_next_dirty_cmma(slots, cur_gfn + 1);
+ /* Reached the end of memory or of the buffer, stop */
+ if ((next_gfn >= mem_end) ||
+ (next_gfn - args->start_gfn >= bufsize))
+ return 0;
+ cur_gfn++;
+ /* Reached the end of the current memslot, take the next one. */
+ if (cur_gfn - ms->base_gfn >= ms->npages) {
+ ms = gfn_to_memslot(kvm, cur_gfn);
+ if (!ms)
+ return 0;
+ }
+ }
+ return 0;
+}
+
+/*
* 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;
@@ -1514,22 +1616,18 @@ static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
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;
+ unsigned long bufsize;
+ int srcu_idx, peek, ret;
+ u8 *values;
- if (unlikely(!kvm->arch.use_cmma))
+ if (!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)
+ if (!peek && !kvm->arch.migration_mode)
return -EINVAL;
/* CMMA is disabled or was not used, or the buffer has length zero */
bufsize = min(args->count, KVM_S390_CMMA_SIZE_MAX);
@@ -1537,74 +1635,35 @@ static int kvm_s390_get_cmma_bits(struct kvm *kvm,
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);
+ /* We are not peeking, and there are no dirty pages */
+ if (!peek && !atomic64_read(&kvm->arch.cmma_dirty_pages)) {
+ memset(args, 0, sizeof(*args));
+ return 0;
}
- res = vmalloc(bufsize);
- if (!res)
+ values = vmalloc(bufsize);
+ if (!values)
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) & 0x43;
- /*
- * 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++;
- }
+ if (peek)
+ ret = kvm_s390_peek_cmma(kvm, args, values, bufsize);
+ else
+ ret = kvm_s390_get_cmma(kvm, args, values, bufsize);
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;
+ if (kvm->arch.migration_mode)
+ args->remaining = atomic64_read(&kvm->arch.cmma_dirty_pages);
+ else
+ args->remaining = 0;
- vfree(res);
- return r;
+ if (copy_to_user((void __user *)args->values, values, args->count))
+ ret = -EFAULT;
+
+ vfree(values);
+ return ret;
}
/*
@@ -2049,10 +2108,6 @@ 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);
}
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 0714bfa..182fd6c 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -954,9 +954,11 @@ static int handle_pfmf(struct kvm_vcpu *vcpu)
return 0;
}
-static inline int do_essa(struct kvm_vcpu *vcpu, const int orc)
+/*
+ * Must be called with relevant read locks held (kvm->mm->mmap_sem, kvm->srcu)
+ */
+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;
@@ -1006,10 +1008,12 @@ static inline int do_essa(struct kvm_vcpu *vcpu, const int orc)
cbrlo[entries] = gfn << PAGE_SHIFT;
}
- if (orc && gfn < ms->bitmap_size) {
- /* 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);
+ if (orc) {
+ struct kvm_memory_slot *ms = gfn_to_memslot(vcpu->kvm, gfn);
+
+ /* Increment only if we are really flipping the bit */
+ if (ms && !test_and_set_bit(gfn - ms->base_gfn, kvm_second_dirty_bitmap(ms)))
+ atomic64_inc(&vcpu->kvm->arch.cmma_dirty_pages);
}
return nappended;
@@ -1038,7 +1042,7 @@ static int handle_essa(struct kvm_vcpu *vcpu)
: ESSA_SET_STABLE_IF_RESIDENT))
return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
- if (likely(!vcpu->kvm->arch.migration_state)) {
+ if (!vcpu->kvm->arch.migration_mode) {
/*
* CMMA is enabled in the KVM settings, but is disabled in
* the SIE block and in the mm_context, and we are not doing
@@ -1066,10 +1070,16 @@ static int handle_essa(struct kvm_vcpu *vcpu)
/* Retry the ESSA instruction */
kvm_s390_retry_instr(vcpu);
} else {
- /* Account for the possible extra cbrl entry */
- i = do_essa(vcpu, orc);
+ int srcu_idx;
+
+ down_read(&vcpu->kvm->mm->mmap_sem);
+ srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
+ i = __do_essa(vcpu, orc);
+ srcu_read_unlock(&vcpu->kvm->srcu, srcu_idx);
+ up_read(&vcpu->kvm->mm->mmap_sem);
if (i < 0)
return i;
+ /* Account for the possible extra cbrl entry */
entries += i;
}
vcpu->arch.sie_block->cbrlo &= PAGE_MASK; /* reset nceo */
--
2.7.4
