[PATCH v7 3/9] KVM: arm/arm64: Re-factor setting the Stage 2 entry to exec on fault

Punit Agrawal punit.agrawal at arm.com
Mon Sep 24 10:45:46 PDT 2018


Stage 2 fault handler marks a page as executable if it is handling an
execution fault or if it was a permission fault in which case the
executable bit needs to be preserved.

The logic to decide if the page should be marked executable is
duplicated for PMD and PTE entries. To avoid creating another copy
when support for PUD hugepages is introduced refactor the code to
share the checks needed to mark a page table entry as executable.

Signed-off-by: Punit Agrawal <punit.agrawal at arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose at arm.com>
Cc: Christoffer Dall <christoffer.dall at arm.com>
Cc: Marc Zyngier <marc.zyngier at arm.com>
---
 virt/kvm/arm/mmu.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 5b76ee204000..ec64d21c6571 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1481,7 +1481,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			  unsigned long fault_status)
 {
 	int ret;
-	bool write_fault, exec_fault, writable, hugetlb = false, force_pte = false;
+	bool write_fault, writable, hugetlb = false, force_pte = false;
+	bool exec_fault, needs_exec;
 	unsigned long mmu_seq;
 	gfn_t gfn = fault_ipa >> PAGE_SHIFT;
 	struct kvm *kvm = vcpu->kvm;
@@ -1606,19 +1607,25 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (exec_fault)
 		invalidate_icache_guest_page(pfn, vma_pagesize);
 
+	/*
+	 * If we took an execution fault we have made the
+	 * icache/dcache coherent above and should now let the s2
+	 * mapping be executable.
+	 *
+	 * Write faults (!exec_fault && FSC_PERM) are orthogonal to
+	 * execute permissions, and we preserve whatever we have.
+	 */
+	needs_exec = exec_fault ||
+		(fault_status == FSC_PERM && stage2_is_exec(kvm, fault_ipa));
+
 	if (hugetlb && vma_pagesize == PMD_SIZE) {
 		pmd_t new_pmd = pfn_pmd(pfn, mem_type);
 		new_pmd = pmd_mkhuge(new_pmd);
 		if (writable)
 			new_pmd = kvm_s2pmd_mkwrite(new_pmd);
 
-		if (exec_fault) {
+		if (needs_exec)
 			new_pmd = kvm_s2pmd_mkexec(new_pmd);
-		} else if (fault_status == FSC_PERM) {
-			/* Preserve execute if XN was already cleared */
-			if (stage2_is_exec(kvm, fault_ipa))
-				new_pmd = kvm_s2pmd_mkexec(new_pmd);
-		}
 
 		ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
 	} else {
@@ -1629,13 +1636,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			mark_page_dirty(kvm, gfn);
 		}
 
-		if (exec_fault) {
+		if (needs_exec)
 			new_pte = kvm_s2pte_mkexec(new_pte);
-		} else if (fault_status == FSC_PERM) {
-			/* Preserve execute if XN was already cleared */
-			if (stage2_is_exec(kvm, fault_ipa))
-				new_pte = kvm_s2pte_mkexec(new_pte);
-		}
 
 		ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte, flags);
 	}
-- 
2.18.0




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