[PATCH v13 03/35] KVM: Use gfn instead of hva for mmu_notifier_retry

[Paolo Bonzini]

On Mon, Oct 30, 2023 at 5:53 PM David Matlack <dmatlack at google.com> wrote:
>
> On 2023-10-27 11:21 AM, Sean Christopherson wrote:
> > From: Chao Peng <chao.p.peng at linux.intel.com>
> >
> > Currently in mmu_notifier invalidate path, hva range is recorded and
> > then checked against by mmu_notifier_retry_hva() in the page fault
> > handling path. However, for the to be introduced private memory, a page
>                           ^^^^^^^^^^^^^^^^^^^^^^^^
>
> Is there a missing word here?

No but there could be missing hyphens ("for the to-be-introduced
private memory"); possibly a "soon" could help parsing and that is
what you were talking about?

> >       if (likely(kvm->mmu_invalidate_in_progress == 1)) {
> > +             kvm->mmu_invalidate_range_start = INVALID_GPA;
> > +             kvm->mmu_invalidate_range_end = INVALID_GPA;
>
> I don't think this is incorrect, but I was a little suprised to see this
> here rather than in end() when mmu_invalidate_in_progress decrements to
> 0.

I think that would be incorrect on the very first start?

> > +     }
> > +}
> > +
> > +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end)
> > +{
> > +     lockdep_assert_held_write(&kvm->mmu_lock);
>
> Does this compile/function on KVM architectures with
> !KVM_HAVE_MMU_RWLOCK?

Yes:

#define lockdep_assert_held_write(l)    \
        lockdep_assert(lockdep_is_held_type(l, 0))

where 0 is the lock-held type used by lock_acquire_exclusive. In turn
is what you get for a spinlock or mutex, in addition to a rwlock or
rwsem that is taken for write.

Instead, lockdep_assert_held() asserts that the lock is taken without
asserting a particular lock-held type.

> > @@ -834,6 +851,12 @@ void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start,
>
> Let's add a lockdep_assert_held_write(&kvm->mmu_lock) here too while
> we're at it?

Yes, good idea.

Paolo