KVM: arm64: Try PMD block mappings if PUD mappings are not supported

When userspace uses hugetlbfs for the VM memory, user_mem_abort() tries to
use the same block size to map the faulting IPA in stage 2. If stage 2
cannot the same block mapping because the block size doesn't fit in the
memslot or the memslot is not properly aligned, user_mem_abort() will fall
back to a page mapping, regardless of the block size. We can do better for
PUD backed hugetlbfs by checking if a PMD block mapping is supported before
deciding to use a page.

vma_pagesize is an unsigned long, use 1UL instead of 1ULL when assigning
its value.
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200910133351.118191-1-alexandru.elisei@arm.com

arch/arm64/kvm/mmu.c

@@ -779,16 +779,25 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	else
 		vma_shift = PAGE_SHIFT;
 
-	vma_pagesize = 1ULL << vma_shift;
 	if (logging_active ||
-	    (vma->vm_flags & VM_PFNMAP) ||
-	    !fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize)) {
+	    (vma->vm_flags & VM_PFNMAP)) {
 		force_pte = true;
-		vma_pagesize = PAGE_SIZE;
+		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;
+		vma_shift = PAGE_SHIFT;
 	}
 
+	vma_pagesize = 1UL << vma_shift;
 	if (vma_pagesize == PMD_SIZE || vma_pagesize == PUD_SIZE)
-		fault_ipa &= huge_page_mask(hstate_vma(vma));
+		fault_ipa &= ~(vma_pagesize - 1);
 
 	gfn = fault_ipa >> PAGE_SHIFT;
 	mmap_read_unlock(current->mm);