* [PATCH] kvm: nVMX: VMCLEAR should not cause the vCPU to shut down
@ 2017-03-02 20:41 Jim Mattson
2017-03-03 16:12 ` Radim Krčmář
0 siblings, 1 reply; 3+ messages in thread
From: Jim Mattson @ 2017-03-02 20:41 UTC (permalink / raw)
To: kvm; +Cc: Jim Mattson
VMCLEAR should silently ignore a failure to clear the launch state of
the VMCS referenced by the operand.
Signed-off-by: Jim Mattson <jmattson@google.com>
---
arch/x86/kvm/vmx.c | 22 ++++------------------
1 file changed, 4 insertions(+), 18 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ef4ba71dbb66..bca497a92541 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7259,9 +7259,8 @@ static int handle_vmoff(struct kvm_vcpu *vcpu)
static int handle_vmclear(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
+ u32 zero = 0;
gpa_t vmptr;
- struct vmcs12 *vmcs12;
- struct page *page;
if (!nested_vmx_check_permission(vcpu))
return 1;
@@ -7272,22 +7271,9 @@ static int handle_vmclear(struct kvm_vcpu *vcpu)
if (vmptr == vmx->nested.current_vmptr)
nested_release_vmcs12(vmx);
- page = nested_get_page(vcpu, vmptr);
- if (page == NULL) {
- /*
- * For accurate processor emulation, VMCLEAR beyond available
- * physical memory should do nothing at all. However, it is
- * possible that a nested vmx bug, not a guest hypervisor bug,
- * resulted in this case, so let's shut down before doing any
- * more damage:
- */
- kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
- return 1;
- }
- vmcs12 = kmap(page);
- vmcs12->launch_state = 0;
- kunmap(page);
- nested_release_page(page);
+ kvm_write_guest(vcpu->kvm,
+ vmptr + offsetof(struct vmcs12, launch_state),
+ &zero, sizeof(zero));
nested_free_vmcs02(vmx, vmptr);
--
2.12.0.rc1.440.g5b76565f74-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] kvm: nVMX: VMCLEAR should not cause the vCPU to shut down
2017-03-02 20:41 [PATCH] kvm: nVMX: VMCLEAR should not cause the vCPU to shut down Jim Mattson
@ 2017-03-03 16:12 ` Radim Krčmář
2017-03-03 16:46 ` Jim Mattson
0 siblings, 1 reply; 3+ messages in thread
From: Radim Krčmář @ 2017-03-03 16:12 UTC (permalink / raw)
To: Jim Mattson; +Cc: kvm
2017-03-02 12:41-0800, Jim Mattson:
> VMCLEAR should silently ignore a failure to clear the launch state of
> the VMCS referenced by the operand.
>
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---
> arch/x86/kvm/vmx.c | 22 ++++------------------
> 1 file changed, 4 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index ef4ba71dbb66..bca497a92541 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -7259,9 +7259,8 @@ static int handle_vmoff(struct kvm_vcpu *vcpu)
> static int handle_vmclear(struct kvm_vcpu *vcpu)
> {
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> + u32 zero = 0;
> gpa_t vmptr;
> - struct vmcs12 *vmcs12;
> - struct page *page;
>
> if (!nested_vmx_check_permission(vcpu))
> return 1;
> @@ -7272,22 +7271,9 @@ static int handle_vmclear(struct kvm_vcpu *vcpu)
> if (vmptr == vmx->nested.current_vmptr)
> nested_release_vmcs12(vmx);
>
> - page = nested_get_page(vcpu, vmptr);
> - if (page == NULL) {
> - /*
> - * For accurate processor emulation, VMCLEAR beyond available
> - * physical memory should do nothing at all. However, it is
> - * possible that a nested vmx bug, not a guest hypervisor bug,
> - * resulted in this case, so let's shut down before doing any
> - * more damage:
> - */
(Consciously introducing bugs in order to somewhat mitigate possible
bugs is not desirable.)
> - kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
> - return 1;
> - }
> - vmcs12 = kmap(page);
> - vmcs12->launch_state = 0;
> - kunmap(page);
> - nested_release_page(page);
> + kvm_write_guest(vcpu->kvm,
I have changed this line to
kvm_vcpu_write_guest(vcpu
and applied to kvm/queue (planning to merge in 4.11-rc2).
The change makes a difference if the guest is using VMX inside SMM and I
don't see a reason to avoid the SMM address space in that case.
Let me know what you think,
thanks.
> + vmptr + offsetof(struct vmcs12, launch_state),
> + &zero, sizeof(zero));
(Could have also been kvm_vcpu_write_guest_page(), but that is only
performance gain.)
>
> nested_free_vmcs02(vmx, vmptr);
>
> --
> 2.12.0.rc1.440.g5b76565f74-goog
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] kvm: nVMX: VMCLEAR should not cause the vCPU to shut down
2017-03-03 16:12 ` Radim Krčmář
@ 2017-03-03 16:46 ` Jim Mattson
0 siblings, 0 replies; 3+ messages in thread
From: Jim Mattson @ 2017-03-03 16:46 UTC (permalink / raw)
To: Radim Krčmář; +Cc: kvm list
That sounds good to me.
Thanks!
--jim
On Fri, Mar 3, 2017 at 8:12 AM, Radim Krčmář <rkrcmar@redhat.com> wrote:
> 2017-03-02 12:41-0800, Jim Mattson:
>> VMCLEAR should silently ignore a failure to clear the launch state of
>> the VMCS referenced by the operand.
>>
>> Signed-off-by: Jim Mattson <jmattson@google.com>
>> ---
>> arch/x86/kvm/vmx.c | 22 ++++------------------
>> 1 file changed, 4 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index ef4ba71dbb66..bca497a92541 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -7259,9 +7259,8 @@ static int handle_vmoff(struct kvm_vcpu *vcpu)
>> static int handle_vmclear(struct kvm_vcpu *vcpu)
>> {
>> struct vcpu_vmx *vmx = to_vmx(vcpu);
>> + u32 zero = 0;
>> gpa_t vmptr;
>> - struct vmcs12 *vmcs12;
>> - struct page *page;
>>
>> if (!nested_vmx_check_permission(vcpu))
>> return 1;
>> @@ -7272,22 +7271,9 @@ static int handle_vmclear(struct kvm_vcpu *vcpu)
>> if (vmptr == vmx->nested.current_vmptr)
>> nested_release_vmcs12(vmx);
>>
>> - page = nested_get_page(vcpu, vmptr);
>> - if (page == NULL) {
>> - /*
>> - * For accurate processor emulation, VMCLEAR beyond available
>> - * physical memory should do nothing at all. However, it is
>> - * possible that a nested vmx bug, not a guest hypervisor bug,
>> - * resulted in this case, so let's shut down before doing any
>> - * more damage:
>> - */
>
> (Consciously introducing bugs in order to somewhat mitigate possible
> bugs is not desirable.)
>
>> - kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
>> - return 1;
>> - }
>> - vmcs12 = kmap(page);
>> - vmcs12->launch_state = 0;
>> - kunmap(page);
>> - nested_release_page(page);
>> + kvm_write_guest(vcpu->kvm,
>
> I have changed this line to
>
> kvm_vcpu_write_guest(vcpu
>
> and applied to kvm/queue (planning to merge in 4.11-rc2).
>
> The change makes a difference if the guest is using VMX inside SMM and I
> don't see a reason to avoid the SMM address space in that case.
> Let me know what you think,
>
> thanks.
>
>> + vmptr + offsetof(struct vmcs12, launch_state),
>> + &zero, sizeof(zero));
>
> (Could have also been kvm_vcpu_write_guest_page(), but that is only
> performance gain.)
>
>>
>> nested_free_vmcs02(vmx, vmptr);
>>
>> --
>> 2.12.0.rc1.440.g5b76565f74-goog
>>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2017-03-03 16:55 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2017-03-02 20:41 [PATCH] kvm: nVMX: VMCLEAR should not cause the vCPU to shut down Jim Mattson
2017-03-03 16:12 ` Radim Krčmář
2017-03-03 16:46 ` Jim Mattson
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