[Qemu-devel] [PATCH 42/48] mmu-hash*: Correctly mask RPN from hash PTE

[David Gibson <david@gibson.dropbear.id.au>]

BEHAVIOUR CHANGE

At present we take the whole of word 1 of the hash PTE as the real page
number used to calculate the translated address.  This is incorrect,
because it leaves the flags from the low bits of PTE word 1 in place in the
rpm.  We mostly get away with that because the value is later masked by
TARGET_PAGE_MASK.

More recent 64-bit CPUs also have a small number of flag bits (PP0 and
KEY) in the top bits of PTE word 1.  Any guest which used those bits would
fail with the current code.

This patch fixes the problem by correctly masking out the RPN field of
PTE word 1.  This is safe, even for older CPUs which didn't have PP0 and
KEY, because although the RPN notionally extended to the very top of PTE
word 1, none of those CPUs actually implemented that many real address
bits.

We add analogous masking to the 32-bit code, even though it also doesn't
have the high flag bits, for consistency and clarity.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 target-ppc/mmu-hash32.c |    2 +-
 target-ppc/mmu-hash64.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/target-ppc/mmu-hash32.c b/target-ppc/mmu-hash32.c
index e5ee29b..07e9b8c 100644
--- a/target-ppc/mmu-hash32.c
+++ b/target-ppc/mmu-hash32.c
@@ -346,7 +346,7 @@ static hwaddr ppc_hash32_htab_lookup(CPUPPCState *env,
 static hwaddr ppc_hash32_pte_raddr(target_ulong sr, ppc_hash_pte32_t pte,
                                    target_ulong eaddr)
 {
-    hwaddr rpn = pte.pte1;
+    hwaddr rpn = pte.pte1 & HPTE32_R_RPN;
     hwaddr mask = ~TARGET_PAGE_MASK;
 
     return (rpn & ~mask) | (eaddr & mask);
diff --git a/target-ppc/mmu-hash64.c b/target-ppc/mmu-hash64.c
index 5e168d5..d986c0f 100644
--- a/target-ppc/mmu-hash64.c
+++ b/target-ppc/mmu-hash64.c
@@ -365,7 +365,7 @@ static hwaddr ppc_hash64_htab_lookup(CPUPPCState *env,
 static hwaddr ppc_hash64_pte_raddr(ppc_slb_t *slb, ppc_hash_pte64_t pte,
                                    target_ulong eaddr)
 {
-    hwaddr rpn = pte.pte1;
+    hwaddr rpn = pte.pte1 & HPTE64_R_RPN;
     /* FIXME: Add support for SLLP extended page sizes */
     int target_page_bits = (slb->vsid & SLB_VSID_L)
         ? TARGET_PAGE_BITS_16M : TARGET_PAGE_BITS;
-- 
1.7.10.4