Hi Will,
Thanks for having a look.
On Thu, Nov 17, 2022 at 05:49:52PM +0000, Will Deacon wrote:
> On Wed, Nov 16, 2022 at 04:56:55PM +0000, Oliver Upton wrote:
[...]
> > -static inline void kvm_pgtable_walk_begin(void) {}
> > -static inline void kvm_pgtable_walk_end(void) {}
> > +static inline void kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker)
> > +{
> > + /*
> > + * Due to the lack of RCU (or a similar protection scheme), only
> > + * non-shared table walkers are allowed in the hypervisor.
> > + */
> > + WARN_ON(walker->flags & KVM_PGTABLE_WALK_SHARED);
> > +}
>
> I think it would be better to propagate the error to the caller rather
> than WARN here.
I'd really like to warn somewhere though since we're rather fscked at
this point. Keeping that WARN close to the exceptional condition would
help w/ debugging.
Were you envisioning bubbling the error all the way back up (i.e. early
return from kvm_pgtable_walk())?
I had really only intended these to indirect lock acquisition/release,
so the error handling on the caller side feels weird:
static inline int kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker)
{
if (WARN_ON(walker->flags & KVM_PGTABLE_WALK_SHARED))
return -EPERM;
return 0;
}
r = kvm_pgtable_walk_begin()
if (r)
return r;
r = _kvm_pgtable_walk();
kvm_pgtable_walk_end();
> Since you're rejigging things anyway, can you have this
> function return int?
If having this is a strong motivator I can do a v4.
--
Thanks,
Oliver
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