* [PATCH] KVM: PPC: set IN_GUEST_MODE before checking requests
@ 2012-08-23 1:03 Scott Wood
2012-09-25 7:44 ` Alexander Graf
0 siblings, 1 reply; 3+ messages in thread
From: Scott Wood @ 2012-08-23 1:03 UTC (permalink / raw)
To: Alexander Graf; +Cc: kvm-ppc, kvm
Avoid a race as described in the code comment.
Also remove a related smp_wmb() from booke's kvmppc_prepare_to_enter().
I can't see any reason for it, and the book3s_pr version doesn't have it.
Signed-off-by: Scott Wood <scottwood@freescale.com>
---
arch/powerpc/kvm/booke.c | 1 -
arch/powerpc/kvm/powerpc.c | 14 +++++++++-----
2 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 5f0476a..88711f8 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -674,7 +674,6 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
out:
vcpu->mode = OUTSIDE_GUEST_MODE;
- smp_wmb();
return ret;
}
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 32d217c..3d460a0 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -78,7 +78,16 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
break;
}
+ vcpu->mode = IN_GUEST_MODE;
+
+ /*
+ * Reading vcpu->requests must happen after setting vcpu->mode,
+ * so we don't miss a request because the requester sees
+ * OUTSIDE_GUEST_MODE and assumes we'll be checking requests
+ * before next entering the guest (and thus doesn't IPI).
+ */
smp_mb();
+
if (vcpu->requests) {
/* Make sure we process requests preemptable */
local_irq_enable();
@@ -111,11 +120,6 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
#endif
kvm_guest_enter();
-
- /* Going into guest context! Yay! */
- vcpu->mode = IN_GUEST_MODE;
- smp_wmb();
-
break;
}
--
1.7.9.5
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] KVM: PPC: set IN_GUEST_MODE before checking requests
2012-08-23 1:03 [PATCH] KVM: PPC: set IN_GUEST_MODE before checking requests Scott Wood
@ 2012-09-25 7:44 ` Alexander Graf
2012-09-25 15:25 ` Scott Wood
0 siblings, 1 reply; 3+ messages in thread
From: Alexander Graf @ 2012-09-25 7:44 UTC (permalink / raw)
To: Scott Wood; +Cc: kvm-ppc, kvm
On 23.08.2012, at 03:03, Scott Wood wrote:
> Avoid a race as described in the code comment.
>
> Also remove a related smp_wmb() from booke's kvmppc_prepare_to_enter().
> I can't see any reason for it, and the book3s_pr version doesn't have it.
>
> Signed-off-by: Scott Wood <scottwood@freescale.com>
Does this patch address your comments on the previous pull request?
Applied to kvm-ppc-next.
Alex
> ---
> arch/powerpc/kvm/booke.c | 1 -
> arch/powerpc/kvm/powerpc.c | 14 +++++++++-----
> 2 files changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 5f0476a..88711f8 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -674,7 +674,6 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
>
> out:
> vcpu->mode = OUTSIDE_GUEST_MODE;
> - smp_wmb();
> return ret;
> }
>
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 32d217c..3d460a0 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -78,7 +78,16 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
> break;
> }
>
> + vcpu->mode = IN_GUEST_MODE;
> +
> + /*
> + * Reading vcpu->requests must happen after setting vcpu->mode,
> + * so we don't miss a request because the requester sees
> + * OUTSIDE_GUEST_MODE and assumes we'll be checking requests
> + * before next entering the guest (and thus doesn't IPI).
> + */
> smp_mb();
> +
> if (vcpu->requests) {
> /* Make sure we process requests preemptable */
> local_irq_enable();
> @@ -111,11 +120,6 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
> #endif
>
> kvm_guest_enter();
> -
> - /* Going into guest context! Yay! */
> - vcpu->mode = IN_GUEST_MODE;
> - smp_wmb();
> -
> break;
> }
>
> --
> 1.7.9.5
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] KVM: PPC: set IN_GUEST_MODE before checking requests
2012-09-25 7:44 ` Alexander Graf
@ 2012-09-25 15:25 ` Scott Wood
0 siblings, 0 replies; 3+ messages in thread
From: Scott Wood @ 2012-09-25 15:25 UTC (permalink / raw)
To: Alexander Graf; +Cc: kvm-ppc, kvm
On 09/25/2012 02:44:52 AM, Alexander Graf wrote:
>
> On 23.08.2012, at 03:03, Scott Wood wrote:
>
> > Avoid a race as described in the code comment.
> >
> > Also remove a related smp_wmb() from booke's
> kvmppc_prepare_to_enter().
> > I can't see any reason for it, and the book3s_pr version doesn't
> have it.
> >
> > Signed-off-by: Scott Wood <scottwood@freescale.com>
>
> Does this patch address your comments on the previous pull request?
It addresses the comments on the vcpu->mode race... I don't remember if
I had any other comments. :-)
-Scott
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-08-23 1:03 [PATCH] KVM: PPC: set IN_GUEST_MODE before checking requests Scott Wood
2012-09-25 7:44 ` Alexander Graf
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