[Qemu-devel] [PULL 13/26] target-s390x: mvc_fast_memset: access memory through softmmu

[Alexander Graf <agraf@suse.de>]

From: Aurelien Jarno <aurelien@aurel32.net>

mvc_fast_memset is bypassing the softmmu functions, getting the
physical address using the mmu_translate function and accessing the
corresponding physical memory. This prevents watchpoints to work
correctly.

Instead use the tlb_vaddr_to_host function to get the host address
corresponding to the guest address through the softmmu code and fallback
to the byte level code in case the corresponding address is not in the
QEMU TLB or being examined through a watchpoint. As a bonus it works
even for area crossing pages by splitting the are into chunks contained
in a single page, bringing some performances improvements.

At the same time change the name of the function to fast_memset as it's
not specific to mvc and use the same argument order as the C memset
function.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
 target-s390x/mem_helper.c | 73 +++++++++++++++++++++--------------------------
 1 file changed, 32 insertions(+), 41 deletions(-)

diff --git a/target-s390x/mem_helper.c b/target-s390x/mem_helper.c
index b8d3a5f..947359b 100644
--- a/target-s390x/mem_helper.c
+++ b/target-s390x/mem_helper.c
@@ -65,30 +65,30 @@ static inline uint64_t adj_len_to_page(uint64_t len, uint64_t addr)
     return len;
 }
 
-#ifndef CONFIG_USER_ONLY
-static void mvc_fast_memset(CPUS390XState *env, uint32_t l, uint64_t dest,
-                            uint8_t byte)
+static void fast_memset(CPUS390XState *env, uint64_t dest, uint8_t byte,
+                        uint32_t l)
 {
-    S390CPU *cpu = s390_env_get_cpu(env);
-    hwaddr dest_phys;
-    hwaddr len = l;
-    void *dest_p;
-    uint64_t asc = env->psw.mask & PSW_MASK_ASC;
-    int flags;
-
-    if (mmu_translate(env, dest, 1, asc, &dest_phys, &flags, true)) {
-        cpu_stb_data(env, dest, byte);
-        cpu_abort(CPU(cpu), "should never reach here");
+    int mmu_idx = cpu_mmu_index(env);
+
+    while (l > 0) {
+        void *p = tlb_vaddr_to_host(env, dest, MMU_DATA_STORE, mmu_idx);
+        if (p) {
+            /* Access to the whole page in write mode granted.  */
+            int l_adj = adj_len_to_page(l, dest);
+            memset(p, byte, l_adj);
+            dest += l_adj;
+            l -= l_adj;
+        } else {
+            /* We failed to get access to the whole page. The next write
+               access will likely fill the QEMU TLB for the next iteration.  */
+            cpu_stb_data(env, dest, byte);
+            dest++;
+            l--;
+        }
     }
-    dest_phys |= dest & ~TARGET_PAGE_MASK;
-
-    dest_p = cpu_physical_memory_map(dest_phys, &len, 1);
-
-    memset(dest_p, byte, len);
-
-    cpu_physical_memory_unmap(dest_p, 1, len, len);
 }
 
+#ifndef CONFIG_USER_ONLY
 static void mvc_fast_memmove(CPUS390XState *env, uint32_t l, uint64_t dest,
                              uint64_t src)
 {
@@ -154,19 +154,11 @@ uint32_t HELPER(xc)(CPUS390XState *env, uint32_t l, uint64_t dest,
     HELPER_LOG("%s l %d dest %" PRIx64 " src %" PRIx64 "\n",
                __func__, l, dest, src);
 
-#ifndef CONFIG_USER_ONLY
     /* xor with itself is the same as memset(0) */
-    if ((l > 32) && (src == dest) &&
-        (src & TARGET_PAGE_MASK) == ((src + l) & TARGET_PAGE_MASK)) {
-        mvc_fast_memset(env, l + 1, dest, 0);
-        return 0;
-    }
-#else
     if (src == dest) {
-        memset(g2h(dest), 0, l + 1);
+        fast_memset(env, dest, 0, l + 1);
         return 0;
     }
-#endif
 
     for (i = 0; i <= l; i++) {
         x = cpu_ldub_data(env, dest + i) ^ cpu_ldub_data(env, src + i);
@@ -208,24 +200,23 @@ void HELPER(mvc)(CPUS390XState *env, uint32_t l, uint64_t dest, uint64_t src)
     HELPER_LOG("%s l %d dest %" PRIx64 " src %" PRIx64 "\n",
                __func__, l, dest, src);
 
+    /* mvc with source pointing to the byte after the destination is the
+       same as memset with the first source byte */
+    if (dest == (src + 1)) {
+        fast_memset(env, dest, cpu_ldub_data(env, src), l + 1);
+        return;
+    }
 #ifndef CONFIG_USER_ONLY
     if ((l > 32) &&
         (src & TARGET_PAGE_MASK) == ((src + l) & TARGET_PAGE_MASK) &&
-        (dest & TARGET_PAGE_MASK) == ((dest + l) & TARGET_PAGE_MASK)) {
-        if (dest == (src + 1)) {
-            mvc_fast_memset(env, l + 1, dest, cpu_ldub_data(env, src));
-            return;
-        } else if ((src & TARGET_PAGE_MASK) != (dest & TARGET_PAGE_MASK)) {
-            mvc_fast_memmove(env, l + 1, dest, src);
-            return;
-        }
+        (dest & TARGET_PAGE_MASK) == ((dest + l) & TARGET_PAGE_MASK) &&
+        (src & TARGET_PAGE_MASK) != (dest & TARGET_PAGE_MASK)) {
+        mvc_fast_memmove(env, l + 1, dest, src);
+        return;
     }
 #else
-    if (dest == (src + 1)) {
-        memset(g2h(dest), cpu_ldub_data(env, src), l + 1);
-        return;
     /* mvc and memmove do not behave the same when areas overlap! */
-    } else if ((dest < src) || (src + l < dest)) {
+    if ((dest < src) || (src + l < dest)) {
         memmove(g2h(dest), g2h(src), l + 1);
         return;
     }
-- 
1.7.12.4