KVM: arm64: Use fallback mapping sizes for contiguous huge page sizes

Although huge pages can be created out of multiple contiguous PMDs
or PTEs, the corresponding sizes are not supported at Stage-2 yet.

Instead of failing the mapping, fall back to the nearer supported
mapping size (CONT_PMD to PMD and CONT_PTE to PTE respectively).

Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Gavin Shan <gshan@redhat.com>
[maz: rewritten commit message]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201025230626.18501-1-gshan@redhat.com

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index a816cb8..e431d2d 100644 (file)
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -787,14 +787,26 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
                vma_shift = PAGE_SHIFT;
        }
 
-       if (vma_shift == PUD_SHIFT &&
-           !fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE))
-              vma_shift = PMD_SHIFT;
-
-       if (vma_shift == PMD_SHIFT &&
-           !fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) {
-               force_pte = true;
+       switch (vma_shift) {
+       case PUD_SHIFT:
+               if (fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE))
+                       break;
+               fallthrough;
+       case CONT_PMD_SHIFT:
+               vma_shift = PMD_SHIFT;
+               fallthrough;
+       case PMD_SHIFT:
+               if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE))
+                       break;
+               fallthrough;
+       case CONT_PTE_SHIFT:
                vma_shift = PAGE_SHIFT;
+               force_pte = true;
+               fallthrough;
+       case PAGE_SHIFT:
+               break;
+       default:
+               WARN_ONCE(1, "Unknown vma_shift %d", vma_shift);
        }
 
        vma_pagesize = 1UL << vma_shift;