In the migration case, if nested state is set after MSR state, the value
needs to come from the current MSR value.
Signed-off-by: Lei Wang <[email protected]>
Reported-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/vmx/nested.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index f18744f7ff82..58a1fa7defc9 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3381,7 +3381,8 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
vmx->nested.vmcs01_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
if (kvm_mpx_supported() &&
- !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS))
+ (!from_vmentry ||
+ !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS)))
vmx->nested.vmcs01_guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS);
/*
--
2.25.1
On Thu, Apr 21, 2022, Lei Wang wrote:
> In the migration case, if nested state is set after MSR state, the value
> needs to come from the current MSR value.
>
> Signed-off-by: Lei Wang <[email protected]>
> Reported-by: Sean Christopherson <[email protected]>
> ---
> arch/x86/kvm/vmx/nested.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index f18744f7ff82..58a1fa7defc9 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -3381,7 +3381,8 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
> if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
> vmx->nested.vmcs01_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
> if (kvm_mpx_supported() &&
> - !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS))
> + (!from_vmentry ||
Gah, my bad, this isn't correct either. The minor issue is that it should check
vmx->nested.nested_run_pending, not just from_vmentry. If nested state is restored
and a VM-Entry is pending, then the MSRs that were saved+restore were L1's MSRs,
not L2's MSRs.
That won't cause problems because the consumption correctly checks nested_run_pending,
it's just confusing and an unnecessary VMREAD.
But that's a moot point because vmcs01 will not hold the correct value in the SMM
case. Luckily, BNDCFGS is easy to handle because it's unconditionally saved on
VM-Exit, which means that vmcs12 is guaranteed to hold the correct value for both
SMM and state restore (without pending entry) because the pseudo-VM-Exit for both
will always save vmcs02's value into vmcs12.
GUEST_IA32_DEBUGCTL is a much bigger pain because it's conditionally saved on
exit. I think the least awful approach would be to save L2's value into
vmcs01_debugctl prior to the forced exit in vmx_enter_smm(), but that will require
more changes to the state restore flow. Grr.
I'll send patches for both BNDCFGS and IA32_DEBUGCTL, and will take a careful look
at the PKS stuff too. I'm guessing it should follow the BNDCFGS logic.
Sorry for the runaround.
On 5/20/2022 1:59 AM, Sean Christopherson wrote:
> On Thu, Apr 21, 2022, Lei Wang wrote:
>> In the migration case, if nested state is set after MSR state, the value
>> needs to come from the current MSR value.
>>
>> Signed-off-by: Lei Wang <[email protected]>
>> Reported-by: Sean Christopherson <[email protected]>
>> ---
>> arch/x86/kvm/vmx/nested.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>> index f18744f7ff82..58a1fa7defc9 100644
>> --- a/arch/x86/kvm/vmx/nested.c
>> +++ b/arch/x86/kvm/vmx/nested.c
>> @@ -3381,7 +3381,8 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
>> if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
>> vmx->nested.vmcs01_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
>> if (kvm_mpx_supported() &&
>> - !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS))
>> + (!from_vmentry ||
> Gah, my bad, this isn't correct either. The minor issue is that it should check
> vmx->nested.nested_run_pending, not just from_vmentry. If nested state is restored
> and a VM-Entry is pending, then the MSRs that were saved+restore were L1's MSRs,
> not L2's MSRs.
>
> That won't cause problems because the consumption correctly checks nested_run_pending,
> it's just confusing and an unnecessary VMREAD.
>
> But that's a moot point because vmcs01 will not hold the correct value in the SMM
> case. Luckily, BNDCFGS is easy to handle because it's unconditionally saved on
> VM-Exit, which means that vmcs12 is guaranteed to hold the correct value for both
> SMM and state restore (without pending entry) because the pseudo-VM-Exit for both
> will always save vmcs02's value into vmcs12.
>
> GUEST_IA32_DEBUGCTL is a much bigger pain because it's conditionally saved on
> exit. I think the least awful approach would be to save L2's value into
> vmcs01_debugctl prior to the forced exit in vmx_enter_smm(), but that will require
> more changes to the state restore flow. Grr.
>
> I'll send patches for both BNDCFGS and IA32_DEBUGCTL, and will take a careful look
> at the PKS stuff too. I'm guessing it should follow the BNDCFGS logic.
>
> Sorry for the runaround.
Thanks for your detailed reviewing, no need for sorry.
Looking forward to your fix patches.