This is a note to let you know that I've just added the patch titled
KVM: x86: update masterclock values on TSC writes
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-update-masterclock-values-on-tsc-writes.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7f187922ddf6b67f2999a76dcb71663097b75497 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Date: Tue, 4 Nov 2014 21:30:44 -0200
Subject: KVM: x86: update masterclock values on TSC writes
From: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
commit 7f187922ddf6b67f2999a76dcb71663097b75497 upstream.
When the guest writes to the TSC, the masterclock TSC copy must be
updated as well along with the TSC_OFFSET update, otherwise a negative
tsc_timestamp is calculated at kvm_guest_time_update.
Once "if (!vcpus_matched && ka->use_master_clock)" is simplified to
"if (ka->use_master_clock)", the corresponding "if (!ka->use_master_clock)"
becomes redundant, so remove the do_request boolean and collapse
everything into a single condition.
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1237,21 +1237,22 @@ void kvm_track_tsc_matching(struct kvm_v
{
#ifdef CONFIG_X86_64
bool vcpus_matched;
- bool do_request = false;
struct kvm_arch *ka = &vcpu->kvm->arch;
struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
vcpus_matched = (ka->nr_vcpus_matched_tsc + 1 ==
atomic_read(&vcpu->kvm->online_vcpus));
- if (vcpus_matched && gtod->clock.vclock_mode == VCLOCK_TSC)
- if (!ka->use_master_clock)
- do_request = 1;
-
- if (!vcpus_matched && ka->use_master_clock)
- do_request = 1;
-
- if (do_request)
+ /*
+ * Once the masterclock is enabled, always perform request in
+ * order to update it.
+ *
+ * In order to enable masterclock, the host clocksource must be TSC
+ * and the vcpus need to have matched TSCs. When that happens,
+ * perform request to enable masterclock.
+ */
+ if (ka->use_master_clock ||
+ (gtod->clock.vclock_mode == VCLOCK_TSC && vcpus_matched))
kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
trace_kvm_track_tsc(vcpu->vcpu_id, ka->nr_vcpus_matched_tsc,
Patches currently in stable-queue which might be from mtosatti@xxxxxxxxxx are
queue-3.18/kvm-x86-update-masterclock-values-on-tsc-writes.patch
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