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

[Gleb Natapov <gleb@redhat.com>]

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
> 
> --
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--
			Gleb.