Patchwork [V2,1/2] KVM/VMX: Check ept_pointer before flushing ept tlb

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Submitter 蓝天宇
Date Dec. 6, 2018, 7:34 a.m.
Message ID <20181206073437.1995-1-Tianyu.Lan@microsoft.com>
Download mbox | patch
Permalink /patch/673835/
State New
Headers show

Comments

蓝天宇 - Dec. 6, 2018, 7:34 a.m.
From: Lan Tianyu <Tianyu.Lan@microsoft.com>

This patch is to initialize ept_pointer to INVALID_PAGE and check it
before flushing ept tlb. If ept_pointer is invalid, bypass the flush
request.

Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
---
 arch/x86/kvm/vmx.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)
Paolo Bonzini - Dec. 14, 2018, 11 a.m.
On 06/12/18 08:34, lantianyu1986@gmail.com wrote:
> From: Lan Tianyu <Tianyu.Lan@microsoft.com>
> 
> This patch is to initialize ept_pointer to INVALID_PAGE and check it
> before flushing ept tlb. If ept_pointer is invalid, bypass the flush
> request.
> 
> Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>

Can you explain better *why* this patch is needed?  Also, should
vmx->ept_pointer be cleared at reset time, rather than vCPU creation?

Thanks,

Paolo

> ---
>  arch/x86/kvm/vmx.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index c379d0bfdcba..6577ec8cbb0f 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1582,11 +1582,18 @@ static int vmx_hv_remote_flush_tlb(struct kvm *kvm)
>  	/*
>  	 * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs the address of the
>  	 * base of EPT PML4 table, strip off EPT configuration information.
> +	 * If ept_pointer is invalid pointer, bypass the flush request.
>  	 */
>  	if (to_kvm_vmx(kvm)->ept_pointers_match != EPT_POINTERS_MATCH) {
> -		kvm_for_each_vcpu(i, vcpu, kvm)
> +		kvm_for_each_vcpu(i, vcpu, kvm) {
> +			u64 ept_pointer = to_vmx(vcpu)->ept_pointer;
> +
> +			if (!VALID_PAGE(ept_pointer))
> +				continue;
> +
>  			ret |= hyperv_flush_guest_mapping(
> -				to_vmx(kvm_get_vcpu(kvm, i))->ept_pointer & PAGE_MASK);
> +				ept_pointer & PAGE_MASK);
> +		}
>  	} else {
>  		ret = hyperv_flush_guest_mapping(
>  				to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer & PAGE_MASK);
> @@ -11614,6 +11621,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
>  	vmx->pi_desc.nv = POSTED_INTR_VECTOR;
>  	vmx->pi_desc.sn = 1;
>  
> +	vmx->ept_pointer = INVALID_PAGE;
> +
>  	return &vmx->vcpu;
>  
>  free_vmcs:
>
蓝天宇 - Dec. 17, 2018, 2:08 p.m.
On Fri, Dec 14, 2018 at 7:00 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 06/12/18 08:34, lantianyu1986@gmail.com wrote:
> > From: Lan Tianyu <Tianyu.Lan@microsoft.com>
> >
> > This patch is to initialize ept_pointer to INVALID_PAGE and check it
> > before flushing ept tlb. If ept_pointer is invalid, bypass the flush
> > request.
> >
> > Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
>
> Can you explain better *why* this patch is needed?
Yes, hypercall still maybe called when ept_pointers aren't
initialized. Such case happens
during guest boot up when BP works at first and APs aren't activated.

>  Also, should vmx->ept_pointer be cleared at reset time, rather than vCPU creation?
>

Yes, that make sense. Thanks for suggestion.

> Thanks,
>
> Paolo
>
> > ---
> >  arch/x86/kvm/vmx.c | 13 +++++++++++--
> >  1 file changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index c379d0bfdcba..6577ec8cbb0f 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -1582,11 +1582,18 @@ static int vmx_hv_remote_flush_tlb(struct kvm *kvm)
> >       /*
> >        * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs the address of the
> >        * base of EPT PML4 table, strip off EPT configuration information.
> > +      * If ept_pointer is invalid pointer, bypass the flush request.
> >        */
> >       if (to_kvm_vmx(kvm)->ept_pointers_match != EPT_POINTERS_MATCH) {
> > -             kvm_for_each_vcpu(i, vcpu, kvm)
> > +             kvm_for_each_vcpu(i, vcpu, kvm) {
> > +                     u64 ept_pointer = to_vmx(vcpu)->ept_pointer;
> > +
> > +                     if (!VALID_PAGE(ept_pointer))
> > +                             continue;
> > +
> >                       ret |= hyperv_flush_guest_mapping(
> > -                             to_vmx(kvm_get_vcpu(kvm, i))->ept_pointer & PAGE_MASK);
> > +                             ept_pointer & PAGE_MASK);
> > +             }
> >       } else {
> >               ret = hyperv_flush_guest_mapping(
> >                               to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer & PAGE_MASK);
> > @@ -11614,6 +11621,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> >       vmx->pi_desc.nv = POSTED_INTR_VECTOR;
> >       vmx->pi_desc.sn = 1;
> >
> > +     vmx->ept_pointer = INVALID_PAGE;
> > +
> >       return &vmx->vcpu;
> >
> >  free_vmcs:
> >
>

Patch

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c379d0bfdcba..6577ec8cbb0f 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1582,11 +1582,18 @@  static int vmx_hv_remote_flush_tlb(struct kvm *kvm)
 	/*
 	 * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs the address of the
 	 * base of EPT PML4 table, strip off EPT configuration information.
+	 * If ept_pointer is invalid pointer, bypass the flush request.
 	 */
 	if (to_kvm_vmx(kvm)->ept_pointers_match != EPT_POINTERS_MATCH) {
-		kvm_for_each_vcpu(i, vcpu, kvm)
+		kvm_for_each_vcpu(i, vcpu, kvm) {
+			u64 ept_pointer = to_vmx(vcpu)->ept_pointer;
+
+			if (!VALID_PAGE(ept_pointer))
+				continue;
+
 			ret |= hyperv_flush_guest_mapping(
-				to_vmx(kvm_get_vcpu(kvm, i))->ept_pointer & PAGE_MASK);
+				ept_pointer & PAGE_MASK);
+		}
 	} else {
 		ret = hyperv_flush_guest_mapping(
 				to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer & PAGE_MASK);
@@ -11614,6 +11621,8 @@  static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 	vmx->pi_desc.nv = POSTED_INTR_VECTOR;
 	vmx->pi_desc.sn = 1;
 
+	vmx->ept_pointer = INVALID_PAGE;
+
 	return &vmx->vcpu;
 
 free_vmcs: