On 08/14/2012 06:04 PM, Alexander Graf wrote:
> Generic KVM code might want to know whether we are inside guest context
> or outside. It also wants to be able to push us out of guest context.
>
> Add support to the BookE code for the generic vcpu->mode field that describes
> the above states.
>
> Signed-off-by: Alexander Graf <agraf@xxxxxxx>
> ---
> arch/powerpc/kvm/booke.c | 11 +++++++++++
> 1 files changed, 11 insertions(+), 0 deletions(-)
>
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index bcf87fe..70a86c0 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -501,6 +501,15 @@ static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
> continue;
> }
>
> + if (vcpu->mode == EXITING_GUEST_MODE) {
> + r = 1;
> + break;
> + }
> +
> + /* Going into guest context! Yay! */
> + vcpu->mode = IN_GUEST_MODE;
> + smp_wmb();
> +
> break;
> }
Normally on entry to this function mode should be OUTSIDE_GUEST_MODE,
right? How could it possibly be EXITING_GUEST_MODE then, since that
only replaces IN_GUEST_MODE?
This doesn't match what x86 does with mode on entry. Mode is supposed
to be set to IN_GUEST_MODE before requests are checked.
I'm not sure what the point of EXITING_GUEST_MODE is at all, compared to
just waiting until after interrupts are disabled before setting
IN_GUEST_MODE (which we do on ppc, but not on x86 even though it seems
like a trivial change), plus the existing ordering between mode and
requests.
-Scott
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