[Qemu-devel] [PATCH 03/25] s390x/mmu: Fix the handling of the table levels

[Jens Freimann <jfrei@linux.vnet.ibm.com>]

From: Thomas Huth <thuth@linux.vnet.ibm.com>

The current code used a wrong and very confusing way of dealing with
the table levels by introducing a "fake level above current". However,
the real problem was simply that the checks for the region/segment
invalid bit and for the matching region/segment level was done at the
wrong spot in the code - it has to be done after the first table entry
has been looked up instead (e.g. there is also no "invalid" bit in the
ASCE itself and the current "level" has to be the same as the level in
the entry that we just looked up).
Also the entries for the segment table are quite a bit different compared
to the region table entries. So this patch moves the related code into the
function mmu_translate_segment() to make it clear at which table level we
currently are and to get rid of the ugly switch-statement in the function
mmu_translate_region().

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
---
 target-s390x/mmu_helper.c | 115 +++++++++++++++++++---------------------------
 1 file changed, 47 insertions(+), 68 deletions(-)

diff --git a/target-s390x/mmu_helper.c b/target-s390x/mmu_helper.c
index c845cd4..01d819e 100644
--- a/target-s390x/mmu_helper.c
+++ b/target-s390x/mmu_helper.c
@@ -134,92 +134,76 @@ static int mmu_translate_pte(CPUS390XState *env, target_ulong vaddr,
     return 0;
 }
 
-/* Decode EDAT1 segment frame absolute address (1MB page) */
-static int mmu_translate_sfaa(CPUS390XState *env, target_ulong vaddr,
-                              uint64_t asc, uint64_t asce, target_ulong *raddr,
-                              int *flags, int rw)
+#define VADDR_PX    0xff000         /* Page index bits */
+
+/* Decode segment table entry */
+static int mmu_translate_segment(CPUS390XState *env, target_ulong vaddr,
+                                 uint64_t asc, uint64_t st_entry,
+                                 target_ulong *raddr, int *flags, int rw)
 {
-    if (asce & _SEGMENT_ENTRY_INV) {
-        DPRINTF("%s: SEG=0x%" PRIx64 " invalid\n", __func__, asce);
-        trigger_page_fault(env, vaddr, PGM_SEGMENT_TRANS, asc, rw);
-        return -1;
-    }
+    CPUState *cs = CPU(s390_env_get_cpu(env));
+    uint64_t origin, offs, pt_entry;
 
-    if (asce & _SEGMENT_ENTRY_RO) {
+    if (st_entry & _SEGMENT_ENTRY_RO) {
         *flags &= ~PAGE_WRITE;
     }
 
-    *raddr = (asce & 0xfffffffffff00000ULL) | (vaddr & 0xfffff);
-
-    PTE_DPRINTF("%s: SEG=0x%" PRIx64 "\n", __func__, asce);
+    if ((st_entry & _SEGMENT_ENTRY_FC) && (env->cregs[0] & CR0_EDAT)) {
+        /* Decode EDAT1 segment frame absolute address (1MB page) */
+        *raddr = (st_entry & 0xfffffffffff00000ULL) | (vaddr & 0xfffff);
+        PTE_DPRINTF("%s: SEG=0x%" PRIx64 "\n", __func__, st_entry);
+        return 0;
+    }
 
-    return 0;
+    /* Look up 4KB page entry */
+    origin = st_entry & _SEGMENT_ENTRY_ORIGIN;
+    offs  = (vaddr & VADDR_PX) >> 9;
+    pt_entry = ldq_phys(cs->as, origin + offs);
+    PTE_DPRINTF("%s: 0x%" PRIx64 " + 0x%" PRIx64 " => 0x%016" PRIx64 "\n",
+                __func__, origin, offs, pt_entry);
+    return mmu_translate_pte(env, vaddr, asc, pt_entry, raddr, flags, rw);
 }
 
-static int mmu_translate_asce(CPUS390XState *env, target_ulong vaddr,
-                              uint64_t asc, uint64_t asce, int level,
-                              target_ulong *raddr, int *flags, int rw)
+/* Decode region table entries */
+static int mmu_translate_region(CPUS390XState *env, target_ulong vaddr,
+                                uint64_t asc, uint64_t entry, int level,
+                                target_ulong *raddr, int *flags, int rw)
 {
     CPUState *cs = CPU(s390_env_get_cpu(env));
-    uint64_t offs = 0;
-    uint64_t origin;
-    uint64_t new_asce;
+    uint64_t origin, offs, new_entry;
+
+    PTE_DPRINTF("%s: 0x%" PRIx64 "\n", __func__, entry);
 
-    PTE_DPRINTF("%s: 0x%" PRIx64 "\n", __func__, asce);
+    origin = entry & _REGION_ENTRY_ORIGIN;
+    offs = (vaddr >> (17 + 11 * level / 4)) & 0x3ff8;
+
+    new_entry = ldq_phys(cs->as, origin + offs);
+    PTE_DPRINTF("%s: 0x%" PRIx64 " + 0x%" PRIx64 " => 0x%016" PRIx64 "\n",
+                __func__, origin, offs, new_entry);
 
-    if (((level != _ASCE_TYPE_SEGMENT) && (asce & _REGION_ENTRY_INV)) ||
-        ((level == _ASCE_TYPE_SEGMENT) && (asce & _SEGMENT_ENTRY_INV))) {
+    if ((new_entry & _REGION_ENTRY_INV) != 0) {
         /* XXX different regions have different faults */
         DPRINTF("%s: invalid region\n", __func__);
         trigger_page_fault(env, vaddr, PGM_SEGMENT_TRANS, asc, rw);
         return -1;
     }
 
-    if ((level <= _ASCE_TYPE_MASK) && ((asce & _ASCE_TYPE_MASK) != level)) {
+    if ((new_entry & _REGION_ENTRY_TYPE_MASK) != level) {
         trigger_page_fault(env, vaddr, PGM_TRANS_SPEC, asc, rw);
         return -1;
     }
 
-    origin = asce & _ASCE_ORIGIN;
-
-    switch (level) {
-    case _ASCE_TYPE_REGION1 + 4:
-        offs = (vaddr >> 50) & 0x3ff8;
-        break;
-    case _ASCE_TYPE_REGION1:
-        offs = (vaddr >> 39) & 0x3ff8;
-        break;
-    case _ASCE_TYPE_REGION2:
-        offs = (vaddr >> 28) & 0x3ff8;
-        break;
-    case _ASCE_TYPE_REGION3:
-        offs = (vaddr >> 17) & 0x3ff8;
-        break;
-    case _ASCE_TYPE_SEGMENT:
-        offs = (vaddr >> 9) & 0x07f8;
-        origin = asce & _SEGMENT_ENTRY_ORIGIN;
-        break;
-    }
-
     /* XXX region protection flags */
     /* *flags &= ~PAGE_WRITE */
 
-    new_asce = ldq_phys(cs->as, origin + offs);
-    PTE_DPRINTF("%s: 0x%" PRIx64 " + 0x%" PRIx64 " => 0x%016" PRIx64 "\n",
-                __func__, origin, offs, new_asce);
-
     if (level == _ASCE_TYPE_SEGMENT) {
-        /* 4KB page */
-        return mmu_translate_pte(env, vaddr, asc, new_asce, raddr, flags, rw);
-    } else if (level - 4 == _ASCE_TYPE_SEGMENT &&
-               (new_asce & _SEGMENT_ENTRY_FC) && (env->cregs[0] & CR0_EDAT)) {
-        /* 1MB page */
-        return mmu_translate_sfaa(env, vaddr, asc, new_asce, raddr, flags, rw);
-    } else {
-        /* yet another region */
-        return mmu_translate_asce(env, vaddr, asc, new_asce, level - 4, raddr,
-                                  flags, rw);
+        return mmu_translate_segment(env, vaddr, asc, new_entry, raddr, flags,
+                                     rw);
     }
+
+    /* yet another region */
+    return mmu_translate_region(env, vaddr, asc, new_entry, level - 4,
+                                raddr, flags, rw);
 }
 
 static int mmu_translate_asc(CPUS390XState *env, target_ulong vaddr,
@@ -227,7 +211,7 @@ static int mmu_translate_asc(CPUS390XState *env, target_ulong vaddr,
                              int rw)
 {
     uint64_t asce = 0;
-    int level, new_level;
+    int level;
     int r;
 
     switch (asc) {
@@ -251,7 +235,8 @@ static int mmu_translate_asc(CPUS390XState *env, target_ulong vaddr,
         return 0;
     }
 
-    switch (asce & _ASCE_TYPE_MASK) {
+    level = asce & _ASCE_TYPE_MASK;
+    switch (level) {
     case _ASCE_TYPE_REGION1:
         break;
     case _ASCE_TYPE_REGION2:
@@ -280,13 +265,7 @@ static int mmu_translate_asc(CPUS390XState *env, target_ulong vaddr,
         break;
     }
 
-    /* fake level above current */
-    level = asce & _ASCE_TYPE_MASK;
-    new_level = level + 4;
-    asce = (asce & ~_ASCE_TYPE_MASK) | (new_level & _ASCE_TYPE_MASK);
-
-    r = mmu_translate_asce(env, vaddr, asc, asce, new_level, raddr, flags, rw);
-
+    r = mmu_translate_region(env, vaddr, asc, asce, level, raddr, flags, rw);
     if ((rw == 1) && !(*flags & PAGE_WRITE)) {
         trigger_prot_fault(env, vaddr, asc);
         return -1;
-- 
2.1.4