[Qemu-devel] [PATCH] target-ppc: Use right page size with hash table lookup

[Aneesh Kumar K.V]

We look at two sizes specified in ISA (4K, 64K). If not found matching,
we consider it 16MB.

Without this patch we would fail to lookup address above 16MB range.
Below 16MB happened to work before because the kernel have a liner
mapping and we always looked up hash for 0xc000000000000000. The
actual real address was computed by using the 16MB offset
with the real address found with the above hash.

Without Fix:
(gdb) x/16x 0xc000000001000000
0xc000000001000000 <list_entries+453208>:       Cannot access memory at address 
0xc000000001000000
(gdb)

With Fix:
(gdb)  x/16x 0xc000000001000000
0xc000000001000000 <list_entries+453208>:       0x00000000      0x00000000      
0x00000000      0x00000000
0xc000000001000010 <list_entries+453224>:       0x00000000      0x00000000      
0x00000000      0x00000000
0xc000000001000020 <list_entries+453240>:       0x00000000      0x00000000      
0x00000000      0x00000000
0xc000000001000030 <list_entries+453256>:       0x00000000      0x00000000      
0x00000000      0x00000000

Signed-off-by: Aneesh Kumar K.V <address@hidden>
---
 target-ppc/cpu.h        |  1 +
 target-ppc/mmu-hash64.c | 37 ++++++++++++++++++++++++++-----------
 target-ppc/mmu-hash64.h |  3 +++
 3 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
index aae33a9237d7..b706b9fdf6c3 100644
--- a/target-ppc/cpu.h
+++ b/target-ppc/cpu.h
@@ -45,6 +45,7 @@
 # define TARGET_VIRT_ADDR_SPACE_BITS 64
 #endif
 
+#define TARGET_PAGE_BITS_64K 16
 #define TARGET_PAGE_BITS_16M 24
 
 #else /* defined (TARGET_PPC64) */
diff --git a/target-ppc/mmu-hash64.c b/target-ppc/mmu-hash64.c
index b0278c95e1d3..971751f7de89 100644
--- a/target-ppc/mmu-hash64.c
+++ b/target-ppc/mmu-hash64.c
@@ -388,6 +388,24 @@ static hwaddr ppc_hash64_pteg_search(CPUPPCState *env, 
hwaddr hash,
     return -1;
 }
 
+static uint64_t ppc_hash64_page_shift(ppc_slb_t *slb)
+{
+    uint64_t epnshift;
+
+    /* Page size according to the SLB, which we use to generate the
+     * EPN for hash table lookup..  When we implement more recent MMU
+     * extensions this might be different from the actual page size
+     * encoded in the PTE */
+    if ((slb->vsid & SLB_VSID_LLP_MASK) == SLB_VSID_4K) {
+        epnshift = TARGET_PAGE_BITS;
+    } else if ((slb->vsid & SLB_VSID_LLP_MASK) == SLB_VSID_64K) {
+        epnshift = TARGET_PAGE_BITS_64K;
+    } else {
+        epnshift = TARGET_PAGE_BITS_16M;
+    }
+    return epnshift;
+}
+
 static hwaddr ppc_hash64_htab_lookup(CPUPPCState *env,
                                      ppc_slb_t *slb, target_ulong eaddr,
                                      ppc_hash_pte64_t *pte)
@@ -396,12 +414,7 @@ static hwaddr ppc_hash64_htab_lookup(CPUPPCState *env,
     hwaddr hash;
     uint64_t vsid, epnshift, epnmask, epn, ptem;
 
-    /* Page size according to the SLB, which we use to generate the
-     * EPN for hash table lookup..  When we implement more recent MMU
-     * extensions this might be different from the actual page size
-     * encoded in the PTE */
-    epnshift = (slb->vsid & SLB_VSID_L)
-        ? TARGET_PAGE_BITS_16M : TARGET_PAGE_BITS;
+    epnshift = ppc_hash64_page_shift(slb);
     epnmask = ~((1ULL << epnshift) - 1);
 
     if (slb->vsid & SLB_VSID_B) {
@@ -448,12 +461,14 @@ 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 mask;
+    int target_page_bits;
     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;
-    hwaddr mask = (1ULL << target_page_bits) - 1;
-
+    /*
+     * We support 4K, 64K and 16M now
+     */
+    target_page_bits = ppc_hash64_page_shift(slb);
+    mask = (1ULL << target_page_bits) - 1;
     return (rpn & ~mask) | (eaddr & mask);
 }
 
diff --git a/target-ppc/mmu-hash64.h b/target-ppc/mmu-hash64.h
index 49e385db90fb..291750f3e5a5 100644
--- a/target-ppc/mmu-hash64.h
+++ b/target-ppc/mmu-hash64.h
@@ -37,6 +37,9 @@ void ppc_hash64_store_hpte(CPUPPCState *env, target_ulong 
index,
 #define SLB_VSID_C              0x0000000000000080ULL /* class */
 #define SLB_VSID_LP             0x0000000000000030ULL
 #define SLB_VSID_ATTR           0x0000000000000FFFULL
+#define SLB_VSID_LLP_MASK       (SLB_VSID_L | SLB_VSID_LP)
+#define SLB_VSID_4K             0x0000000000000000ULL
+#define SLB_VSID_64K            0x0000000000000110ULL
 
 /*
  * Hash page table definitions
-- 
2.1.0