From: Zachary Amsden <zamsden@redhat.com>
To: KVM <kvm@vger.kernel.org>, Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Glauber Costa <glommer@redhat.com>
Cc: Linux-kernel <linux-kernel@vger.kernel.org>,
Zachary Amsden <zamsden@redhat.com>
Subject: [PATCH 08/18] Fix deep C-state TSC desynchronization
Date: Mon, 12 Jul 2010 16:08:02 -1000 [thread overview]
Message-ID: <1278986892-11733-9-git-send-email-zamsden@redhat.com> (raw)
In-Reply-To: <1278986892-11733-1-git-send-email-zamsden@redhat.com>
When CPUs with unstable TSCs enter deep C-state, TSC may stop
running. This causes us to require resynchronization. Since
we can't tell when this may potentially happen, we assume the
worst by forcing re-compensation for it at every point the VCPU
task is descheduled.
Signed-off-by: Zachary Amsden <zamsden@redhat.com>
---
arch/x86/kvm/x86.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9e71222..0ad6419 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1872,7 +1872,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
}
kvm_x86_ops->vcpu_load(vcpu, cpu);
- if (unlikely(vcpu->cpu != cpu)) {
+ if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) {
/* Make sure TSC doesn't go backwards */
s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :
native_read_tsc() - vcpu->arch.last_host_tsc;
--
1.7.1
next prev parent reply other threads:[~2010-07-13 2:11 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-13 2:07 KVM timekeeping fixes Zachary Amsden
2010-07-13 2:07 ` [PATCH 01/18] Make TSC offset writes non-preemptible Zachary Amsden
2010-07-13 2:07 ` [PATCH 02/18] Fix SVM VMCB reset Zachary Amsden
2010-07-13 2:07 ` [PATCH 03/18] TSC reset compensation Zachary Amsden
2010-07-13 2:07 ` [PATCH 04/18] Robust TSC compensation Zachary Amsden
2010-07-13 2:07 ` [PATCH 05/18] Make cpu_tsc_khz updates use local CPU Zachary Amsden
2010-07-13 2:08 ` [PATCH 06/18] Warn about unstable TSC Zachary Amsden
2010-07-13 2:08 ` [PATCH 07/18] Unify TSC logic Zachary Amsden
2010-07-13 2:08 ` Zachary Amsden [this message]
2010-07-13 2:08 ` [PATCH 09/18] Add helper functions for time computation Zachary Amsden
2010-07-13 2:08 ` [PATCH 10/18] Keep SMP VMs more in sync on unstable TSC Zachary Amsden
2010-07-13 2:08 ` [PATCH 11/18] Perform hardware_enable in CPU_STARTING callback Zachary Amsden
2010-07-13 2:08 ` [PATCH 12/18] Add clock sync request to hardware enable Zachary Amsden
2010-07-13 2:08 ` [PATCH 13/18] Move scale_delta into common header Zachary Amsden
2010-07-13 2:08 ` [PATCH 14/18] Fix a possible backwards warp of kvmclock Zachary Amsden
2010-07-13 2:08 ` [PATCH 15/18] Implement getnsboottime kernel API Zachary Amsden
2010-07-13 2:08 ` [PATCH 16/18] Use getnsboottime in KVM Zachary Amsden
2010-07-13 2:08 ` [PATCH 17/18] Indicate reliable TSC in kvmclock Zachary Amsden
2010-07-13 2:08 ` [PATCH 18/18] Add timekeeping documentation Zachary Amsden
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=1278986892-11733-9-git-send-email-zamsden@redhat.com \
--to=zamsden@redhat.com \
--cc=avi@redhat.com \
--cc=glommer@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mtosatti@redhat.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).