mmu-hash*: Don't update PTE flags when permission is denied

BEHAVIOUR CHANGE

Currently if ppc_hash{32,64}_translate() finds a PTE matching the given
virtual address, it will always update the PTE's R & C (Referenced and
Changed) bits.  This happens even if the PTE's permissions mean we are
about to deny the translation.

This is clearly a bug, although we get away with it because:
  a) It will only incorrectly set, never reset the bits, which should not
cause guest correctness problems.
  b) Linux guests never use the R & C bits anyway.

This patch fixes the behaviour, only updating R & C when access is granted
by the PTE.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 7 insertions, 5 deletions

diff --git a/target-ppc/mmu-hash64.c b/target-ppc/mmu-hash64.c
index 2e109f4896..f7aa352a9b 100644
--- a/target-ppc/mmu-hash64.c
+++ b/target-ppc/mmu-hash64.c
@@ -460,15 +460,17 @@ static int ppc_hash64_translate(CPUPPCState *env, struct mmu_ctx_hash64 *ctx,
     ctx->raddr = pte.pte1;
     ctx->prot = access;
     ret = ppc_hash64_check_prot(ctx->prot, rwx);
-    if (ret == 0) {
-        /* Access granted */
-        LOG_MMU("PTE access granted !\n");
-    } else {
+
+    if (ret) {
         /* Access right violation */
         LOG_MMU("PTE access rejected\n");
+        return ret;
     }
 
-    /* Update page flags */
+    LOG_MMU("PTE access granted !\n");
+
+    /* 6. Update PTE referenced and changed bits if necessary */
+
     if (ppc_hash64_pte_update_flags(ctx, &pte.pte1, ret, rwx) == 1) {
         ppc_hash64_store_hpte1(env, pte_offset, pte.pte1);
     }