Re: [PATCH v3 2/2] x86/svm: Use the virtual NMI when available

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/02/2026 10:07 am, Teddy Astie wrote:
> Le 15/02/2026 à 19:24, Abdelkareem Abdelsaamad a écrit :
>> With the Virtual NMI (vNMI), the pending NMI is simply stuffed into the VMCB
>> and handed off to the hardware. There is no need for the artificial tracking
>> of the NMI handling completion with the IRET instruction interception.
>>
>> Adjust the svm_inject_nmi to rather inject the NMIs using the vNMI Hardware
>> accelerated feature when the AMD platform support the vNMI.
>>
>> Adjust the svm_get_interrupt_shadow to check if the vNMI is currently blocked
>> by servicing another in-progress NMI.
>>
>> Signed-off-by: Abdelkareem Abdelsaamad <abdelkareem.abdelsaamad@xxxxxxxxxx>
>> ---
>>   xen/arch/x86/hvm/svm/intr.c | 9 +++++++++
>>   xen/arch/x86/hvm/svm/svm.c  | 5 ++++-
>>   xen/arch/x86/hvm/svm/vmcb.c | 2 ++
>>   3 files changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/xen/arch/x86/hvm/svm/intr.c b/xen/arch/x86/hvm/svm/intr.c
>> index 6453a46b85..3e8959f155 100644
>> --- a/xen/arch/x86/hvm/svm/intr.c
>> +++ b/xen/arch/x86/hvm/svm/intr.c
>> @@ -33,6 +33,15 @@ static void svm_inject_nmi(struct vcpu *v)
>>       u32 general1_intercepts = vmcb_get_general1_intercepts(vmcb);
>>       intinfo_t event;
>>   
>> +    if ( vmcb->_vintr.fields.vnmi_enable )
>> +    {
>> +       if ( !vmcb->_vintr.fields.vnmi_pending &&
>> +            !vmcb->_vintr.fields.vnmi_blocking )
>> +           vmcb->_vintr.fields.vnmi_pending = 1;
>> +
>> +        return;
>> +    }
>> +
> I think you need to update the clearbit for tpr (related to vintr) for 
> the hardware to know that you modified the vnmi_pending bit.

What makes you think this?  The APM states otherwise.

~Andrew