KVM: arm64: Avoid mapping size adjustment on permission fault

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>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20210726153552.1535838-4-maz@kernel.org

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 183c107..116a291 100644 (file)
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1076,9 +1076,14 @@ 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 || device)) {
+               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 */