On Fri, Mar 12, 2021 at 05:32:13AM +0000, Quentin Perret wrote:
> On Thursday 11 Mar 2021 at 19:04:07 (+0000), Will Deacon wrote:
> > On Wed, Mar 10, 2021 at 05:57:47PM +0000, Quentin Perret wrote:
> > > + for (level = pgt->start_level; level < KVM_PGTABLE_MAX_LEVELS; level++) {
> > > + granule = kvm_granule_size(level);
> > > + start = ALIGN_DOWN(addr, granule);
> > > + end = start + granule;
> > > +
> > > + if (!kvm_level_support_block_mappings(level))
> > > + continue;
> > > +
> > > + if (start < range->start || range->end < end)
> > > + continue;
> > > +
> > > + /*
> > > + * Check the presence of existing mappings with incompatible
> > > + * permissions within the current block range, and try one level
> > > + * deeper if one is found.
> > > + */
> > > + ret = kvm_pgtable_walk(pgt, start, granule, &check_perm_walker);
> > > + if (ret != -EEXIST)
> > > + break;
> > > + }
> >
> > Can you write this as a:
> >
> > do {
> > ...
> > } while (level < KVM_PGTABLE_MAX_LEVELS && ret == -EEXIST);
> >
> > loop?
>
> I tried it but found it a little less pretty -- the pre-assignment of
> level and the increment at the end make it really feel like a for loop
> to me:
>
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -1098,26 +1098,23 @@ int kvm_pgtable_stage2_find_range(struct kvm_pgtable *pgt, u64 addr,
> return ret;
> attr &= KVM_PTE_LEAF_S2_COMPAT_MASK;
>
> - for (level = pgt->start_level; level < KVM_PGTABLE_MAX_LEVELS; level++) {
> + ret = -EEXIST;
> + level = pgt->start_level;
> + do {
> granule = kvm_granule_size(level);
> start = ALIGN_DOWN(addr, granule);
> end = start + granule;
>
> - if (!kvm_level_support_block_mappings(level))
> - continue;
> -
> - if (start < range->start || range->end < end)
> - continue;
Urgh, yes, sorry, I hadn't appreciated what a mess it causes for these guys.
Stick with the 'for' loop.
Will
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