From: Luis Henriques <henrix@sapo.pt>
To: Avi Kivity <avi@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org,
Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: Problem with kvm on -tip
Date: Sat, 11 Apr 2009 20:45:46 +0100 [thread overview]
Message-ID: <20090411194546.GA12126@hades.domain.com> (raw)
In-Reply-To: <49E08857.2090503@redhat.com>
Hi,
On Sat, Apr 11, 2009 at 03:08:55PM +0300, Avi Kivity wrote:
>
> This might be fixed by the attached patch.
I confirm that the patch you sent removes the warnings but does it really solve
the issue? (Sorry, I really do not know this code so I might be saying something
really stupid.)
What I understand from your patch is that the only portion of code that needs
protection is the __get_cpu_var(). If this is true then a patch like the one
below would do a better job. But I am not sure that nothing else needs
protection since the code immediately following the preempt_enable (in your
patch) is an invocation to local_irq_save()...
---
arch/x86/kvm/x86.c | 10 +++++++---
1 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8ca100a..cf918b5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -626,13 +626,17 @@ static void kvm_write_guest_time(struct kvm_vcpu *v)
unsigned long flags;
struct kvm_vcpu_arch *vcpu = &v->arch;
void *shared_kaddr;
+ uint32_t tsc_khz;
if ((!vcpu->time_page))
return;
- if (unlikely(vcpu->hv_clock_tsc_khz != __get_cpu_var(cpu_tsc_khz))) {
- kvm_set_time_scale(__get_cpu_var(cpu_tsc_khz), &vcpu->hv_clock);
- vcpu->hv_clock_tsc_khz = __get_cpu_var(cpu_tsc_khz);
+ preempt_disable();
+ tsc_khz = __get_cpu_var(cpu_tsc_khz);
+ preempt_enable();
+ if (unlikely(vcpu->hv_clock_tsc_khz != tsc_khz)) {
+ kvm_set_time_scale(tsc_khz, &vcpu->hv_clock);
+ vcpu->hv_clock_tsc_khz = tsc_khz;
}
/* Keep irq disabled to prevent changes to the clock */
--
1.6.2.1
next prev parent reply other threads:[~2009-04-11 19:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-09 21:07 Problem with kvm on -tip Luis Henriques
2009-04-10 11:58 ` Ingo Molnar
2009-04-10 15:33 ` Jeremy Fitzhardinge
2009-04-11 12:08 ` Avi Kivity
2009-04-11 19:45 ` Luis Henriques [this message]
2009-04-12 11:53 ` Avi Kivity
2009-04-12 12:54 ` Luis Henriques
2009-04-12 12:42 ` Ingo Molnar
2009-04-12 12:46 ` Avi Kivity
2009-04-14 7:58 ` Peter Zijlstra
2009-04-14 8:20 ` Avi Kivity
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