Re: [PATCH 2/4] KVM: arm64: Don't serialize if the access flag isn't set

[Oliver Upton]

Hi Ricardo,

Thanks for having a look.

On Tue, Nov 29, 2022 at 12:52:12PM -0800, Ricardo Koller wrote:
> On Tue, Nov 29, 2022 at 07:19:44PM +0000, Oliver Upton wrote:

[...]

> > +	ret = stage2_update_leaf_attrs(pgt, addr, 1, KVM_PTE_LEAF_ATTR_LO_S2_AF, 0,
> > +				       &pte, NULL, 0);
> > +	if (!ret)
> > +		dsb(ishst);
> 
> At the moment, the only reason for stage2_update_leaf_attrs() to not
> update the PTE is if it's not valid:
> 
> 	if (!kvm_pte_valid(pte))
> 			return 0;
> 
> I guess you could check that as well:
> 
> +	if (!ret || kvm_pte_valid(pte))
> +		dsb(ishst);

Thanks for catching this.

Instead of pivoting on the returned PTE value, how about we return
-EAGAIN from the early return in stage2_attr_walker()? It would better
match the pattern used elsewhere in the pgtable code.

--
Thanks,
Oliver