On Thu, Aug 02, 2012 at 05:14:02PM -0300, Marcelo Tosatti wrote:
> On Tue, Jul 31, 2012 at 04:19:02PM +0530, Nikunj A. Dadhania wrote:
> > From: Nikunj A. Dadhania <nikunj@xxxxxxxxxxxxxxxxxx>
> >
> > PV-Flush guest would indicate to flush on enter, flush the TLB before
> > entering and exiting the guest.
> >
> > Signed-off-by: Nikunj A. Dadhania <nikunj@xxxxxxxxxxxxxxxxxx>
> > ---
> > arch/x86/kvm/x86.c | 23 +++++++----------------
> > 1 files changed, 7 insertions(+), 16 deletions(-)
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 580abcf..a67e971 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -1557,20 +1557,9 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
> > &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
> > }
> >
> > -static void kvm_set_atomic(u64 *addr, u64 old, u64 new)
> > -{
> > - int loop = 1000000;
> > - while (1) {
> > - if (cmpxchg(addr, old, new) == old)
> > - break;
> > - loop--;
> > - if (!loop) {
> > - pr_info("atomic cur: %lx old: %lx new: %lx\n",
> > - *addr, old, new);
> > - break;
> > - }
> > - }
> > -}
> > +#define VS_NOT_IN_GUEST (0)
> > +#define VS_IN_GUEST (1 << KVM_VCPU_STATE_IN_GUEST_MODE)
> > +#define VS_SHOULD_FLUSH (1 << KVM_VCPU_STATE_SHOULD_FLUSH)
> >
> > static void kvm_set_vcpu_state(struct kvm_vcpu *vcpu)
> > {
> > @@ -1584,7 +1573,8 @@ static void kvm_set_vcpu_state(struct kvm_vcpu *vcpu)
> > kaddr = kmap_atomic(vcpu->arch.v_state.vs_page);
> > kaddr += vcpu->arch.v_state.vs_offset;
> > vs = kaddr;
> > - kvm_set_atomic(&vs->state, 0, 1 << KVM_VCPU_STATE_IN_GUEST_MODE);
> > + if (xchg(&vs->state, VS_IN_GUEST) == VS_SHOULD_FLUSH)
> > + kvm_x86_ops->tlb_flush(vcpu);
> > kunmap_atomic(kaddr);
> > }
> >
> > @@ -1600,7 +1590,8 @@ static void kvm_clear_vcpu_state(struct kvm_vcpu *vcpu)
> > kaddr = kmap_atomic(vcpu->arch.v_state.vs_page);
> > kaddr += vcpu->arch.v_state.vs_offset;
> > vs = kaddr;
> > - kvm_set_atomic(&vs->state, 1 << KVM_VCPU_STATE_IN_GUEST_MODE, 0);
> > + if (xchg(&vs->state, VS_NOT_IN_GUEST) == VS_SHOULD_FLUSH)
> > + kvm_x86_ops->tlb_flush(vcpu);
> > kunmap_atomic(kaddr);
> > }
>
> Nevermind the early comment (the other comments on that message are
> valid).
Ah, so the pseucode mentions flush-on-exit because we can be clearing
the flag on xchg. Setting KVM_REQ_TLB_FLUSH instead should be enough
(please verify).
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