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@xxxxxxxxxx>
> ---
> 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
>
