[Qemu-devel] [PATCH-for-4.2 v2 2/6] s390x/tcg: Rework MMU selection for instruction fetches

[David Hildenbrand <david@redhat.com>]

Instructions are always fetched from primary address space, except when
in home address mode. Perform the selection directly in cpu_mmu_index().

get_mem_index() is only used to perform data access, instructions are
fetched via cpu_lduw_code(), which translates to cpu_mmu_index(env, true).

We don't care about restricting the access permissions of the TLB
entries anymore, as we no longer enter PRIMARY entries into the
SECONDARY MMU. Cleanup related code a bit.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 target/s390x/cpu.h        |  7 +++++++
 target/s390x/mmu_helper.c | 38 +++++++++++++++-----------------------
 2 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index a606547b4d..c34992bb2e 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -332,6 +332,13 @@ static inline int cpu_mmu_index(CPUS390XState *env, bool ifetch)
         return MMU_REAL_IDX;
     }
 
+    if (ifetch) {
+        if ((env->psw.mask & PSW_MASK_ASC) == PSW_ASC_HOME) {
+            return MMU_HOME_IDX;
+        }
+        return MMU_PRIMARY_IDX;
+    }
+
     switch (env->psw.mask & PSW_MASK_ASC) {
     case PSW_ASC_PRIMARY:
         return MMU_PRIMARY_IDX;
diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c
index 6e9c4d6151..c34e8d2021 100644
--- a/target/s390x/mmu_helper.c
+++ b/target/s390x/mmu_helper.c
@@ -349,8 +349,9 @@ int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t asc,
 {
     static S390SKeysState *ss;
     static S390SKeysClass *skeyclass;
-    int r = -1;
+    uint64_t asce;
     uint8_t key;
+    int r;
 
     if (unlikely(!ss)) {
         ss = s390_get_skeys_device();
@@ -380,36 +381,21 @@ int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t asc,
 
     if (!(env->psw.mask & PSW_MASK_DAT)) {
         *raddr = vaddr;
-        r = 0;
-        goto out;
+        goto nodat;
     }
 
     switch (asc) {
     case PSW_ASC_PRIMARY:
         PTE_DPRINTF("%s: asc=primary\n", __func__);
-        r = mmu_translate_asce(env, vaddr, asc, env->cregs[1], raddr, flags,
-                               rw, exc);
+        asce = env->cregs[1];
         break;
     case PSW_ASC_HOME:
         PTE_DPRINTF("%s: asc=home\n", __func__);
-        r = mmu_translate_asce(env, vaddr, asc, env->cregs[13], raddr, flags,
-                               rw, exc);
+        asce = env->cregs[13];
         break;
     case PSW_ASC_SECONDARY:
         PTE_DPRINTF("%s: asc=secondary\n", __func__);
-        /*
-         * Instruction: Primary
-         * Data: Secondary
-         */
-        if (rw == MMU_INST_FETCH) {
-            r = mmu_translate_asce(env, vaddr, PSW_ASC_PRIMARY, env->cregs[1],
-                                   raddr, flags, rw, exc);
-            *flags &= ~(PAGE_READ | PAGE_WRITE);
-        } else {
-            r = mmu_translate_asce(env, vaddr, PSW_ASC_SECONDARY, env->cregs[7],
-                                   raddr, flags, rw, exc);
-            *flags &= ~(PAGE_EXEC);
-        }
+        asce = env->cregs[7];
         break;
     case PSW_ASC_ACCREG:
     default:
@@ -417,11 +403,17 @@ int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t asc,
         break;
     }
 
- out:
+    /* perform the DAT translation */
+    r = mmu_translate_asce(env, vaddr, asc, asce, raddr, flags, rw, exc);
+    if (r) {
+        return r;
+    }
+
+nodat:
     /* Convert real address -> absolute address */
     *raddr = mmu_real2abs(env, *raddr);
 
-    if (r == 0 && *raddr < ram_size) {
+    if (*raddr < ram_size) {
         if (skeyclass->get_skeys(ss, *raddr / TARGET_PAGE_SIZE, 1, &key)) {
             trace_get_skeys_nonzero(r);
             return 0;
@@ -441,7 +433,7 @@ int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t asc,
         }
     }
 
-    return r;
+    return 0;
 }
 
 /**
-- 
2.21.0