On Sun, Mar 12, 2023 at 01:01:26PM +0000, Marc Zyngier wrote:
> On Tue, 07 Mar 2023 03:45:54 +0000,
> Ricardo Koller <ricarkol@xxxxxxxxxx> wrote:
> >
> > This is the arm64 counterpart of commit cb00a70bd4b7 ("KVM: x86/mmu:
> > Split huge pages mapped by the TDP MMU during KVM_CLEAR_DIRTY_LOG"),
> > which has the benefit of splitting the cost of splitting a memslot
> > across multiple ioctls.
> >
> > Split huge pages on the range specified using KVM_CLEAR_DIRTY_LOG.
> > And do not split when enabling dirty logging if
> > KVM_DIRTY_LOG_INITIALLY_SET is set.
> >
> > Signed-off-by: Ricardo Koller <ricarkol@xxxxxxxxxx>
> > ---
> > arch/arm64/kvm/mmu.c | 15 ++++++++++++---
> > 1 file changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index 910aea6bbd1e..d54223b5db97 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -1089,8 +1089,8 @@ static void kvm_mmu_split_memory_region(struct kvm *kvm, int slot)
> > * @mask: The mask of pages at offset 'gfn_offset' in this memory
> > * slot to enable dirty logging on
> > *
> > - * Writes protect selected pages to enable dirty logging for them. Caller must
> > - * acquire kvm->mmu_lock.
> > + * Splits selected pages to PAGE_SIZE and then writes protect them to enable
> > + * dirty logging for them. Caller must acquire kvm->mmu_lock.
>
> The code does things in the opposite order...
Fixed the comment.
>
> > */
> > void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
> > struct kvm_memory_slot *slot,
> > @@ -1103,6 +1103,13 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
> > lockdep_assert_held_write(&kvm->mmu_lock);
> >
> > stage2_wp_range(&kvm->arch.mmu, start, end);
> > +
> > + /*
> > + * If initially-all-set mode is not set, then huge-pages were already
> > + * split when enabling dirty logging: no need to do it again.
> > + */
> > + if (kvm_dirty_log_manual_protect_and_init_set(kvm))
>
> This contradicts the comment. Which one is correct?a
Changed the comment.
>
> > + kvm_mmu_split_huge_pages(kvm, start, end);
> > }
> >
> > static void kvm_send_hwpoison_signal(unsigned long address, short lsb)
> > @@ -1889,7 +1896,9 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
> > * this when deleting, moving, disabling dirty logging, or
> > * creating the memslot (a nop). Doing it for deletes makes
> > * sure we don't leak memory, and there's no need to keep the
> > - * cache around for any of the other cases.
> > + * cache around for any of the other cases. Keeping the cache
> > + * is useful for successive KVM_CLEAR_DIRTY_LOG calls, which is
> > + * not handled in this function.
>
> Where is it handled then?
This last sentence doesn't make much sense, so I removed it. CLEAR calls
don't even go through this function.
>
> > */
> > kvm_mmu_free_memory_cache(&kvm->arch.mmu.split_page_cache);
> > }
>
> Thanks,
>
> M.
>
> --
> Without deviation from the norm, progress is not possible.
