| Message ID | 20210517135054.1914802-3-vkuznets@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: nVMX: Fixes for nested state migration when eVMCS is in use | expand |
On Mon, 2021-05-17 at 15:50 +0200, Vitaly Kuznetsov wrote: > Unlike VMREAD/VMWRITE/VMPTRLD, VMCLEAR is a valid instruction when > enlightened VMCS is in use. TLFS has the following brief description: > "The L1 hypervisor can execute a VMCLEAR instruction to transition an > enlightened VMCS from the active to the non-active state". Normally, > this change can be ignored as unmapping active eVMCS can be postponed > until the next VMLAUNCH instruction but in case nested state is migrated > with KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE, keeping eVMCS mapped > may result in its synchronization with VMCS12 and this is incorrect: > L1 hypervisor is free to reuse inactive eVMCS memory for something else. > > Inactive eVMCS after VMCLEAR can just be unmapped. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > --- > arch/x86/kvm/vmx/nested.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > index 3080e00c8f90..ea2869d8b823 100644 > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -5008,6 +5008,8 @@ static int handle_vmclear(struct kvm_vcpu *vcpu) > vmptr + offsetof(struct vmcs12, > launch_state), > &zero, sizeof(zero)); > + } else if (vmx->nested.hv_evmcs && vmptr == vmx->nested.hv_evmcs_vmptr) { > + nested_release_evmcs(vcpu); > } Releasing the eVMCS is a good thing not only for migration but for instance for nested_vmx_fail which could write to current eVMCS even outside of nested mode (there is a bug there but you fixed it in the patch 4). Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> Best regards, Maxim Levitsky > > return nested_vmx_succeed(vcpu);
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 3080e00c8f90..ea2869d8b823 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -5008,6 +5008,8 @@ static int handle_vmclear(struct kvm_vcpu *vcpu) vmptr + offsetof(struct vmcs12, launch_state), &zero, sizeof(zero)); + } else if (vmx->nested.hv_evmcs && vmptr == vmx->nested.hv_evmcs_vmptr) { + nested_release_evmcs(vcpu); } return nested_vmx_succeed(vcpu);
Unlike VMREAD/VMWRITE/VMPTRLD, VMCLEAR is a valid instruction when enlightened VMCS is in use. TLFS has the following brief description: "The L1 hypervisor can execute a VMCLEAR instruction to transition an enlightened VMCS from the active to the non-active state". Normally, this change can be ignored as unmapping active eVMCS can be postponed until the next VMLAUNCH instruction but in case nested state is migrated with KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE, keeping eVMCS mapped may result in its synchronization with VMCS12 and this is incorrect: L1 hypervisor is free to reuse inactive eVMCS memory for something else. Inactive eVMCS after VMCLEAR can just be unmapped. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> --- arch/x86/kvm/vmx/nested.c | 2 ++ 1 file changed, 2 insertions(+)