diff options
| author | Vincent Donnefort <vdonnefort@google.com> | 2023-09-28 18:32:03 +0100 |
|---|---|---|
| committer | Oliver Upton <oliver.upton@linux.dev> | 2023-09-30 17:17:45 +0000 |
| commit | c04bf723ccd639250fa680a0fb4e1ac15bb84c3b (patch) | |
| tree | 5715b340d9151a37ed08603c73bc04f2070b9b5b /arch/arm64/kvm/mmu.c | |
| parent | 909b583f81b5bb5a398d4580543f59b908a86ccc (diff) | |
KVM: arm64: Do not transfer page refcount for THP adjustment
GUP affects a refcount common to all pages forming the THP. There is
therefore no need to move the refcount from a tail to the head page.
Under the hood it decrements and increments the same counter.
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230928173205.2826598-2-vdonnefort@google.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Diffstat (limited to 'arch/arm64/kvm/mmu.c')
| -rw-r--r-- | arch/arm64/kvm/mmu.c | 20 |
1 files changed, 0 insertions, 20 deletions
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 587a104f66c3..de5e5148ef5d 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1295,28 +1295,8 @@ transparent_hugepage_adjust(struct kvm *kvm, struct kvm_memory_slot *memslot, if (sz < PMD_SIZE) return PAGE_SIZE; - /* - * The address we faulted on is backed by a transparent huge - * page. However, because we map the compound huge page and - * not the individual tail page, we need to transfer the - * refcount to the head page. We have to be careful that the - * THP doesn't start to split while we are adjusting the - * refcounts. - * - * We are sure this doesn't happen, because mmu_invalidate_retry - * was successful and we are holding the mmu_lock, so if this - * THP is trying to split, it will be blocked in the mmu - * notifier before touching any of the pages, specifically - * before being able to call __split_huge_page_refcount(). - * - * We can therefore safely transfer the refcount from PG_tail - * to PG_head and switch the pfn from a tail page to the head - * page accordingly. - */ *ipap &= PMD_MASK; - kvm_release_pfn_clean(pfn); pfn &= ~(PTRS_PER_PMD - 1); - get_page(pfn_to_page(pfn)); *pfnp = pfn; return PMD_SIZE; |