Since the KVM dirty page reporting works on guest physical addresses,
we need to clear all of the aliases when a page is migrated, or there
is a risk of losing writes to the aliases that were not cleared.
Note that this is only an issue for manual clearing of the bitmap;
if the bitmap is cleared at the same time as it's retrieved, all
the aliases get cleared correctly.
Reported-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
Fixes: ff4aa11419242c835b03d274f08f797c129ed7ba
Cc: qemu-sta...@nongnu.org
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
accel/kvm/kvm-all.c | 36 ++++++++++++++++++++++--------------
1 file changed, 22 insertions(+), 14 deletions(-)
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index e9e6086..315a915 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -588,8 +588,8 @@ static int kvm_log_clear_one_slot(KVMSlot *mem, int as_id,
uint64_t start, uint6
* satisfy the KVM interface requirement. Firstly, do the start
* page alignment on 64 host pages
*/
- bmap_start = (start - mem->start_addr) & KVM_CLEAR_LOG_MASK;
- start_delta = start - mem->start_addr - bmap_start;
+ bmap_start = start & KVM_CLEAR_LOG_MASK;
+ start_delta = start - bmap_start;
bmap_start /= psize;
/*
@@ -693,8 +693,8 @@ static int kvm_physical_log_clear(KVMMemoryListener *kml,
MemoryRegionSection *section)
{
KVMState *s = kvm_state;
- uint64_t start, size;
- KVMSlot *mem = NULL;
+ uint64_t start, size, offset, count;
+ KVMSlot *mem;
int ret, i;
if (!s->manual_dirty_log_protect) {
@@ -712,22 +712,30 @@ static int kvm_physical_log_clear(KVMMemoryListener *kml,
kvm_slots_lock(kml);
- /* Find any possible slot that covers the section */
for (i = 0; i < s->nr_slots; i++) {
mem = &kml->slots[i];
- if (mem->start_addr <= start &&
- start + size <= mem->start_addr + mem->memory_size) {
+ /* Discard slots that are empty or do not overlap the section */
+ if (!mem->memory_size ||
+ mem->start_addr > start + size - 1 ||
+ start > mem->start_addr + mem->memory_size - 1) {
+ continue;
+ }
+
+ if (start >= mem->start_addr) {
+ /* The slot starts before section or is aligned to it. */
+ offset = start - mem->start_addr;
+ count = MIN(mem->memory_size - offset, size);
+ } else {
+ /* The slot starts after section. */
+ offset = 0;
+ count = MIN(mem->memory_size, size - (mem->start_addr - start));
+ }
+ ret = kvm_log_clear_one_slot(mem, kml->as_id, offset, count);
+ if (ret < 0) {
break;
}
}
- /*
- * We should always find one memslot until this point, otherwise
- * there could be something wrong from the upper layer
- */
- assert(mem && i != s->nr_slots);
- ret = kvm_log_clear_one_slot(mem, kml->as_id, start, size);
-
kvm_slots_unlock(kml);
return ret;
--
1.8.3.1
