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[PULL 18/26] KVM: Disable manual dirty log when dirty ring enabled
From: |
Paolo Bonzini |
Subject: |
[PULL 18/26] KVM: Disable manual dirty log when dirty ring enabled |
Date: |
Thu, 20 May 2021 10:22:49 +0200 |
From: Peter Xu <peterx@redhat.com>
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is for KVM_CLEAR_DIRTY_LOG, which is only
useful for KVM_GET_DIRTY_LOG. Skip enabling it for kvm dirty ring.
More importantly, KVM_DIRTY_LOG_INITIALLY_SET will not wr-protect all the pages
initially, which is against how kvm dirty ring is used - there's no way for kvm
dirty ring to re-protect a page before it's notified as being written first
with a GFN entry in the ring! So when KVM_DIRTY_LOG_INITIALLY_SET is enabled
with dirty ring, we'll see silent data loss after migration.
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210506160549.130416-10-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
accel/kvm/kvm-all.c | 37 +++++++++++++++++++++++--------------
1 file changed, 23 insertions(+), 14 deletions(-)
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 5afe15ae66..e1a6c7c89b 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2131,20 +2131,29 @@ static int kvm_init(MachineState *ms)
s->coalesced_pio = s->coalesced_mmio &&
kvm_check_extension(s, KVM_CAP_COALESCED_PIO);
- dirty_log_manual_caps =
- kvm_check_extension(s, KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2);
- dirty_log_manual_caps &= (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE |
- KVM_DIRTY_LOG_INITIALLY_SET);
- s->manual_dirty_log_protect = dirty_log_manual_caps;
- if (dirty_log_manual_caps) {
- ret = kvm_vm_enable_cap(s, KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2, 0,
- dirty_log_manual_caps);
- if (ret) {
- warn_report("Trying to enable capability %"PRIu64" of "
- "KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 but failed. "
- "Falling back to the legacy mode. ",
- dirty_log_manual_caps);
- s->manual_dirty_log_protect = 0;
+ /*
+ * KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is not needed when dirty ring is
+ * enabled. More importantly, KVM_DIRTY_LOG_INITIALLY_SET will assume no
+ * page is wr-protected initially, which is against how kvm dirty ring is
+ * usage - kvm dirty ring requires all pages are wr-protected at the very
+ * beginning. Enabling this feature for dirty ring causes data corruption.
+ */
+ if (!s->kvm_dirty_ring_size) {
+ dirty_log_manual_caps =
+ kvm_check_extension(s, KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2);
+ dirty_log_manual_caps &= (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE |
+ KVM_DIRTY_LOG_INITIALLY_SET);
+ s->manual_dirty_log_protect = dirty_log_manual_caps;
+ if (dirty_log_manual_caps) {
+ ret = kvm_vm_enable_cap(s, KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2, 0,
+ dirty_log_manual_caps);
+ if (ret) {
+ warn_report("Trying to enable capability %"PRIu64" of "
+ "KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 but failed. "
+ "Falling back to the legacy mode. ",
+ dirty_log_manual_caps);
+ s->manual_dirty_log_protect = 0;
+ }
}
}
--
2.31.1
- [PULL 12/26] KVM: Create the KVMSlot dirty bitmap on flag changes, (continued)
- [PULL 12/26] KVM: Create the KVMSlot dirty bitmap on flag changes, Paolo Bonzini, 2021/05/20
- [PULL 02/26] configure: check for submodules if --with-git-submodules=ignore, Paolo Bonzini, 2021/05/20
- [PULL 07/26] object: add more commands to preconfig mode, Paolo Bonzini, 2021/05/20
- [PULL 05/26] i386/cpu: Expose AVX_VNNI instruction to guest, Paolo Bonzini, 2021/05/20
- [PULL 21/26] meson: Set implicit_include_directories to false, Paolo Bonzini, 2021/05/20
- [PULL 20/26] tests/qtest/fuzz: Fix build failure, Paolo Bonzini, 2021/05/20
- [PULL 08/26] qtest: add a QOM object for qtest, Paolo Bonzini, 2021/05/20
- [PULL 15/26] KVM: Simplify dirty log sync in kvm_set_phys_mem, Paolo Bonzini, 2021/05/20
- [PULL 19/26] KVM: Dirty ring support, Paolo Bonzini, 2021/05/20
- [PULL 09/26] KVM: do not allow setting properties at runtime, Paolo Bonzini, 2021/05/20
- [PULL 18/26] KVM: Disable manual dirty log when dirty ring enabled,
Paolo Bonzini <=
- [PULL 06/26] meson: bump submodule to 0.57.2, Paolo Bonzini, 2021/05/20
- [PULL 22/26] remove qemu-options* from root directory, Paolo Bonzini, 2021/05/20
- [PULL 16/26] KVM: Cache kvm slot dirty bitmap size, Paolo Bonzini, 2021/05/20
- [PULL 25/26] qemu-config: load modules when instantiating option groups, Paolo Bonzini, 2021/05/20
- [PULL 10/26] memory: Introduce log_sync_global() to memory listener, Paolo Bonzini, 2021/05/20
- [PULL 11/26] KVM: Use a big lock to replace per-kml slots_lock, Paolo Bonzini, 2021/05/20
- [PULL 17/26] KVM: Add dirty-ring-size property, Paolo Bonzini, 2021/05/20
- [PULL 13/26] KVM: Provide helper to get kvm dirty log, Paolo Bonzini, 2021/05/20
- [PULL 23/26] replication: move include out of root directory, Paolo Bonzini, 2021/05/20
- [PULL 26/26] scsi-generic: pass max_segments via max_iov field in BlockLimits, Paolo Bonzini, 2021/05/20