1 files changed, 64 insertions, 22 deletions

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index f605514395a1..dee3dbd98712 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1595,6 +1595,63 @@ static void kvm_send_hwpoison_signal(unsigned long address,
 	send_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, current);
 }
 
+static bool fault_supports_stage2_pmd_mappings(struct kvm_memory_slot *memslot,
+					       unsigned long hva)
+{
+	gpa_t gpa_start, gpa_end;
+	hva_t uaddr_start, uaddr_end;
+	size_t size;
+
+	size = memslot->npages * PAGE_SIZE;
+
+	gpa_start = memslot->base_gfn << PAGE_SHIFT;
+	gpa_end = gpa_start + size;
+
+	uaddr_start = memslot->userspace_addr;
+	uaddr_end = uaddr_start + size;
+
+	/*
+	 * Pages belonging to memslots that don't have the same alignment
+	 * within a PMD for userspace and IPA cannot be mapped with stage-2
+	 * PMD entries, because we'll end up mapping the wrong pages.
+	 *
+	 * Consider a layout like the following:
+	 *
+	 *    memslot->userspace_addr:
+	 *    +-----+--------------------+--------------------+---+
+	 *    |abcde|fgh  Stage-1 PMD    |    Stage-1 PMD   tv|xyz|
+	 *    +-----+--------------------+--------------------+---+
+	 *
+	 *    memslot->base_gfn << PAGE_SIZE:
+	 *      +---+--------------------+--------------------+-----+
+	 *      |abc|def  Stage-2 PMD    |    Stage-2 PMD     |tvxyz|
+	 *      +---+--------------------+--------------------+-----+
+	 *
+	 * If we create those stage-2 PMDs, we'll end up with this incorrect
+	 * mapping:
+	 *   d -> f
+	 *   e -> g
+	 *   f -> h
+	 */
+	if ((gpa_start & ~S2_PMD_MASK) != (uaddr_start & ~S2_PMD_MASK))
+		return false;
+
+	/*
+	 * Next, let's make sure we're not trying to map anything not covered
+	 * by the memslot. This means we have to prohibit PMD size mappings
+	 * for the beginning and end of a non-PMD aligned and non-PMD sized
+	 * memory slot (illustrated by the head and tail parts of the
+	 * userspace view above containing pages 'abcde' and 'xyz',
+	 * respectively).
+	 *
+	 * Note that it doesn't matter if we do the check using the
+	 * userspace_addr or the base_gfn, as both are equally aligned (per
+	 * the check above) and equally sized.
+	 */
+	return (hva & S2_PMD_MASK) >= uaddr_start &&
+	       (hva & S2_PMD_MASK) + S2_PMD_SIZE <= uaddr_end;
+}
+
 static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			  struct kvm_memory_slot *memslot, unsigned long hva,
 			  unsigned long fault_status)
@@ -1621,6 +1678,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		return -EFAULT;
 	}
 
+	if (!fault_supports_stage2_pmd_mappings(memslot, hva))
+		force_pte = true;
+
+	if (logging_active)
+		force_pte = true;
+
 	/* Let's check if we will get back a huge page backed by hugetlbfs */
 	down_read(&current->mm->mmap_sem);
 	vma = find_vma_intersection(current->mm, hva, hva + 1);
@@ -1637,28 +1700,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 */
 	if ((vma_pagesize == PMD_SIZE ||
 	     (vma_pagesize == PUD_SIZE && kvm_stage2_has_pud(kvm))) &&
-	    !logging_active) {
+	    !force_pte) {
 		gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT;
-	} else {
-		/*
-		 * Fallback to PTE if it's not one of the Stage 2
-		 * supported hugepage sizes or the corresponding level
-		 * doesn't exist
-		 */
-		vma_pagesize = PAGE_SIZE;
-
-		/*
-		 * Pages belonging to memslots that don't have the same
-		 * alignment for userspace and IPA cannot be mapped using
-		 * block descriptors even if the pages belong to a THP for
-		 * the process, because the stage-2 block descriptor will
-		 * cover more than a single THP and we loose atomicity for
-		 * unmapping, updates, and splits of the THP or other pages
-		 * in the stage-2 block range.
-		 */
-		if ((memslot->userspace_addr & ~PMD_MASK) !=
-		    ((memslot->base_gfn << PAGE_SHIFT) & ~PMD_MASK))
-			force_pte = true;
 	}
 	up_read(&current->mm->mmap_sem);
 
@@ -1697,7 +1740,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		 * should not be mapped with huge pages (it introduces churn
 		 * and performance degradation), so force a pte mapping.
 		 */
-		force_pte = true;
 		flags |= KVM_S2_FLAG_LOGGING_ACTIVE;
 
 		/*