Re: [PATCH v13 09/21] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA

[Paul Durrant]

On 19/02/2024 21:49, Sean Christopherson wrote:
> On Thu, Feb 15, 2024, Paul Durrant wrote:
> > @@ -319,7 +340,16 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
> >   
> >   int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len)
> >   {
> > -	return __kvm_gpc_refresh(gpc, gpc->gpa, len);
> > +	unsigned long uhva = gpc->uhva;
> > +
> > +	/*
> > +	 * If the GPA is valid then invalidate the HVA, otherwise
> > +	 * __kvm_gpc_refresh() will fail its strict either/or address check.
> > +	 */
>
> It's not just to make the strict check happy, though that's obviously the direct
> motivation, it's so that there's one root of truth.  The strict check is there to
> enforce that behavior and to make it  more clear to readers that it's an either/or
> situation.
>
> > +	if (!kvm_is_error_gpa(gpc->gpa))
> > +		uhva = KVM_HVA_ERR_BAD;
>
> This would be a good time to use a ternary operator.
>
> 	/*
> 	 * If the GPA is valid then ignore the HVA, as a cache can be GPA-based
> 	 * or HVA-based, not both.  For GPA-based caches, the HVA will be
> 	 * recomputed during refresh if necessary.
> 	 */
> 	unsigned long uhva = kvm_is_error_gpa(gpc->gpa) ? gpc->uhva :
> 							  KVM_HVA_ERR_BAD;

Ok. I thought that actually looked a little less neat in this case, but 
I'll change.