[PATCH 2/5] KVM: arm64: Avoid mapping size adjustment on permission fault

[Marc Zyngier <maz@kernel.org>]

Since we only support PMD-sized mappings for THP, getting
a permission fault on a level that results in a mapping
being larger than PAGE_SIZE is a sure indication that we have
already upgraded our mapping to a PMD.

In this case, there is no need to try and parse userspace page
tables, as the fault information already tells us everything.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/mmu.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index db6314b93e99..c036a480ca27 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1088,9 +1088,14 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * If we are not forced to use page mapping, check if we are
 	 * backed by a THP and thus use block mapping if possible.
 	 */
-	if (vma_pagesize == PAGE_SIZE && !(force_pte || device))
-		vma_pagesize = transparent_hugepage_adjust(kvm, memslot, hva,
-							   &pfn, &fault_ipa);
+	if (vma_pagesize == PAGE_SIZE && !force_pte) {
+		if (fault_status == FSC_PERM && fault_granule > PAGE_SIZE)
+			vma_pagesize = fault_granule;
+		else
+			vma_pagesize = transparent_hugepage_adjust(kvm, memslot,
+								   hva, &pfn,
+								   &fault_ipa);
+	}
 
 	if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) {
 		/* Check the VMM hasn't introduced a new VM_SHARED VMA */
-- 
2.30.2