From: Peter Xu <peterx@redhat.com>
To: qemu-devel@nongnu.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Keqian Zhu <zhukeqian1@huawei.com>,
Hyman <huangy81@chinatelecom.cn>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
peterx@redhat.com
Subject: [PATCH v6 09/10] KVM: Disable manual dirty log when dirty ring enabled
Date: Wed, 24 Mar 2021 14:39:53 -0400 [thread overview]
Message-ID: <20210324183954.345629-10-peterx@redhat.com> (raw)
In-Reply-To: <20210324183954.345629-1-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>
---
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 8baa002c009..daf59836ae2 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2169,20 +2169,29 @@ static int kvm_init(MachineState *ms)
}
}
- 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_enabled) {
+ 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;
+ }
}
}
--
2.26.2
next prev parent reply other threads:[~2021-03-24 18:47 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-24 18:39 [PATCH v6 00/10] KVM: Dirty ring support (QEMU part) Peter Xu
2021-03-24 18:39 ` [PATCH v6 01/10] memory: Introduce log_sync_global() to memory listener Peter Xu
2021-03-24 18:39 ` [PATCH v6 02/10] KVM: Use a big lock to replace per-kml slots_lock Peter Xu
2021-03-24 18:39 ` [PATCH v6 03/10] KVM: Create the KVMSlot dirty bitmap on flag changes Peter Xu
2021-03-24 18:39 ` [PATCH v6 04/10] KVM: Provide helper to get kvm dirty log Peter Xu
2021-03-24 18:39 ` [PATCH v6 05/10] KVM: Provide helper to sync dirty bitmap from slot to ramblock Peter Xu
2021-03-24 18:39 ` [PATCH v6 06/10] KVM: Simplify dirty log sync in kvm_set_phys_mem Peter Xu
2021-03-24 18:39 ` [PATCH v6 07/10] KVM: Cache kvm slot dirty bitmap size Peter Xu
2021-03-24 18:39 ` [PATCH v6 08/10] KVM: Add dirty-gfn-count property Peter Xu
2021-03-24 18:39 ` Peter Xu [this message]
2021-03-24 18:41 ` [PATCH v6 10/10] KVM: Dirty ring support Peter Xu
2021-04-29 21:07 ` [PATCH v6 00/10] KVM: Dirty ring support (QEMU part) Peter Xu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210324183954.345629-10-peterx@redhat.com \
--to=peterx@redhat.com \
--cc=dgilbert@redhat.com \
--cc=huangy81@chinatelecom.cn \
--cc=pbonzini@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=zhukeqian1@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).