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 <[email protected]>
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
>
>
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