Re: [PATCH v2 2/8] x86/hvm: Only populate info->cr2 for #PF in hvm_get_pending_event()

[Jinoh Kang <jinoh.kang.kr@xxxxxxxxx>]

On 8/30/23 22:41, Jan Beulich wrote:
> On 24.08.2023 17:25, Jinoh Kang wrote:
>> Prepare for an upcoming patch that overloads the 'cr2' field for #DB.
> 
> Seeing the subsequent change and the fact that earlier on Andrew didn't
> need such an adjustment, I'm afraid I can't see the need for this change,
> and the one sentence above also doesn't answer the "Why?", but only the
> "What?"

This is part of the hvm_monitor_interrupt() fix (patch 4), which would
otherwise get CR2 value (instead of PENDING_DBG) even for #DB.

I might have been overzealous, though, since there is no known (broken)
use for VM_EVENT_REASON_INTERRUPT in the first place.

> 
> Jan
> 
>> --- a/xen/arch/x86/hvm/hvm.c
>> +++ b/xen/arch/x86/hvm/hvm.c
>> @@ -503,9 +503,14 @@ void hvm_migrate_pirqs(struct vcpu *v)
>>  
>>  static bool hvm_get_pending_event(struct vcpu *v, struct x86_event *info)
>>  {
>> -    info->cr2 = v->arch.hvm.guest_cr[2];
>> +    if ( !alternative_call(hvm_funcs.get_pending_event, v, info) )
>> +        return false;
>> +
>> +    if ( info->type == X86_EVENTTYPE_HW_EXCEPTION &&
>> +         info->vector == X86_EXC_PF )
>> +        info->cr2 = v->arch.hvm.guest_cr[2];
>>  
>> -    return alternative_call(hvm_funcs.get_pending_event, v, info);
>> +    return true;
>>  }
>>  
>>  void hvm_do_resume(struct vcpu *v)
> 

-- 
Sincerely,
Jinoh Kang