Re: [PATCH V2 2/4] KVM: SVM: Fix nested NPF injection to set PFERR_GUEST_{PAGE,FINAL}_MASK

[Sean Christopherson <seanjc@google.com>]

On Tue, Feb 24, 2026, Sean Christopherson wrote:
> > diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> > index 37eba7dafd14f..f148c92b606ba 100644
> > --- a/arch/x86/kvm/mmu/paging_tmpl.h
> > +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> > @@ -385,18 +385,12 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
> >  		real_gpa = kvm_translate_gpa(vcpu, mmu, gfn_to_gpa(table_gfn),
> >  					     nested_access, &walker->fault);
> >  
> > -		/*
> > -		 * FIXME: This can happen if emulation (for of an INS/OUTS
> > -		 * instruction) triggers a nested page fault.  The exit
> > -		 * qualification / exit info field will incorrectly have
> > -		 * "guest page access" as the nested page fault's cause,
> > -		 * instead of "guest page structure access".  To fix this,
> > -		 * the x86_exception struct should be augmented with enough
> > -		 * information to fix the exit_qualification or exit_info_1
> > -		 * fields.
> > -		 */
> > -		if (unlikely(real_gpa == INVALID_GPA))
> > +		if (unlikely(real_gpa == INVALID_GPA)) {
> > +#if PTTYPE != PTTYPE_EPT
> 
> I would rather swap the order of patches two and three, so that we end up with
> a "positive" if-statement.  I.e. add EPT first so that we get (spoiler alert):
> 
> #if PTTYPE == PTTYPE_EPT
> 			walker->fault.exit_qualification |= EPT_VIOLATION_GVA_IS_VALID;
> #else
> 			walker->fault.error_code |= PFERR_GUEST_PAGE_MASK;
> #endif

Scratch this comment, I got my walkers confused.