Re: [PATCH v4] KVM: VMX: Execute WBINVD to keep data consistency with assigned devices

Gleb Natapov
2010-06-28T09:32:06Z

On Mon, Jun 28, 2010 at 12:27:22PM +0300, Avi Kivity wrote:
> nOn 06/28/2010 11:42 AM, Sheng Yang wrote:
> >Some guest device driver may leverage the "Non-Snoop" I/O, and explicitly
> >WBINVD or CLFLUSH to a RAM space. Since migration may occur before WBINVD or
> >CLFLUSH, we need to maintain data consistency either by:
> >1: flushing cache (wbinvd) when the guest is scheduled out if there is no
> >wbinvd exit, or
> >2: execute wbinvd on all dirty physical CPUs when guest wbinvd exits.
> >
> >
> >+int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu)
> >+{
> >+ if (need_emulate_wbinvd(vcpu)&& kvm_x86_ops->has_wbinvd_exit()) {
> >+ smp_call_function_many(vcpu->arch.wbinvd_dirty_mask,
> >+ wbinvd_ipi, NULL, 1);
> >+ cpumask_clear(vcpu->arch.wbinvd_dirty_mask);
> >+ } else
> >+ wbinvd();
> >+ return X86EMUL_CONTINUE;
> >+}
> >+EXPORT_SYMBOL_GPL(kvm_emulate_wbinvd);
>
> Why check for has_wbinvd_exit()? If it's false, we don't get here anyway.
>
> If !need_emulate_wbinvd(), why call wbinvd()?
>
>
The function is called from emulator too. I guess that is why.

> >+
> > int emulate_clts(struct kvm_vcpu *vcpu)
> > {
> > kvm_x86_ops->set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
> >@@ -5255,6 +5287,7 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
> > vcpu->arch.time_page = NULL;
> > }
> >
> >+ free_cpumask_var(vcpu->arch.wbinvd_dirty_mask);
> > fx_free(vcpu);
> > kvm_x86_ops->vcpu_free(vcpu);
> > }
> >@@ -5262,7 +5295,16 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
> > struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
> > unsigned int id)
> > {
> >- return kvm_x86_ops->vcpu_create(kvm, id);
> >+ struct kvm_vcpu *vcpu = kvm_x86_ops->vcpu_create(kvm, id);
> >+
> >+ if (IS_ERR(vcpu))
> >+ return vcpu;
> >+
> >+ if (!zalloc_cpumask_var(&vcpu->arch.wbinvd_dirty_mask, GFP_KERNEL)) {
> >+ kvm_x86_ops->vcpu_free(vcpu);
> >+ return ERR_PTR(-ENOMEM);
> >+ }
> >+ return vcpu;
> > }
> >
>
> Better place is kvm_arch_vcpu_init().
>
> --
> error compiling committee.c: too many arguments to function
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html

--
Gleb.