[Qemu-devel] [PATCH 04/15] target-s390x: mvc_fast_memmove: access memory through softmmu

[Aurelien Jarno <aurelien@aurel32.net>]

mvc_fast_memmove is bypassing the softmmu functions, getting the
physical source and destination addresses 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 addresses
corresponding to the guest source and destination addresses through the
softmmu code and fallback to the byte level code in case the
corresponding address are 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. We can therefore remove the 8-byte
loads/stores method, as it is now quite unlikely to be used.

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

Cc: Alexander Graf <agraf@suse.de>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
---
 target-s390x/mem_helper.c | 84 +++++++++++++++--------------------------------
 1 file changed, 27 insertions(+), 57 deletions(-)

diff --git a/target-s390x/mem_helper.c b/target-s390x/mem_helper.c
index 947359b..6427ee9 100644
--- a/target-s390x/mem_helper.c
+++ b/target-s390x/mem_helper.c
@@ -88,40 +88,33 @@ static void fast_memset(CPUS390XState *env, uint64_t dest, uint8_t byte,
     }
 }
 
-#ifndef CONFIG_USER_ONLY
-static void mvc_fast_memmove(CPUS390XState *env, uint32_t l, uint64_t dest,
-                             uint64_t src)
+static void fast_memmove(CPUS390XState *env, uint64_t dest, uint64_t src,
+                         uint32_t l)
 {
-    S390CPU *cpu = s390_env_get_cpu(env);
-    hwaddr dest_phys;
-    hwaddr src_phys;
-    hwaddr len = l;
-    void *dest_p;
-    void *src_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, 0);
-        cpu_abort(CPU(cpu), "should never reach here");
-    }
-    dest_phys |= dest & ~TARGET_PAGE_MASK;
+    int mmu_idx = cpu_mmu_index(env);
 
-    if (mmu_translate(env, src, 0, asc, &src_phys, &flags, true)) {
-        cpu_ldub_data(env, src);
-        cpu_abort(CPU(cpu), "should never reach here");
+    while (l > 0) {
+        void *src_p = tlb_vaddr_to_host(env, src, MMU_DATA_LOAD, mmu_idx);
+        void *dest_p = tlb_vaddr_to_host(env, dest, MMU_DATA_STORE, mmu_idx);
+        if (src_p && dest_p) {
+            /* Access to both whole pages granted.  */
+            int l_adj = adj_len_to_page(l, src);
+            l_adj = adj_len_to_page(l_adj, dest);
+            memmove(dest_p, src_p, l_adj);
+            src += l_adj;
+            dest += l_adj;
+            l -= l_adj;
+        } else {
+            /* We failed to get access to one or both whole pages. The next
+               read or write access will likely fill the QEMU TLB for the
+               next iteration.  */
+            cpu_stb_data(env, dest, cpu_ldub_data(env, src));
+            src++;
+            dest++;
+            l--;
+        }
     }
-    src_phys |= src & ~TARGET_PAGE_MASK;
-
-    dest_p = cpu_physical_memory_map(dest_phys, &len, 1);
-    src_p = cpu_physical_memory_map(src_phys, &len, 0);
-
-    memmove(dest_p, src_p, len);
-
-    cpu_physical_memory_unmap(dest_p, 1, len, len);
-    cpu_physical_memory_unmap(src_p, 0, len, len);
 }
-#endif
 
 /* and on array */
 uint32_t HELPER(nc)(CPUS390XState *env, uint32_t l, uint64_t dest,
@@ -194,8 +187,6 @@ uint32_t HELPER(oc)(CPUS390XState *env, uint32_t l, uint64_t dest,
 void HELPER(mvc)(CPUS390XState *env, uint32_t l, uint64_t dest, uint64_t src)
 {
     int i = 0;
-    int x = 0;
-    uint32_t l_64 = (l + 1) / 8;
 
     HELPER_LOG("%s l %d dest %" PRIx64 " src %" PRIx64 "\n",
                __func__, l, dest, src);
@@ -206,32 +197,15 @@ void HELPER(mvc)(CPUS390XState *env, uint32_t l, uint64_t dest, uint64_t src)
         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) &&
-        (src & TARGET_PAGE_MASK) != (dest & TARGET_PAGE_MASK)) {
-        mvc_fast_memmove(env, l + 1, dest, src);
-        return;
-    }
-#else
+
     /* mvc and memmove do not behave the same when areas overlap! */
     if ((dest < src) || (src + l < dest)) {
-        memmove(g2h(dest), g2h(src), l + 1);
+        fast_memmove(env, dest, src, l + 1);
         return;
     }
-#endif
-
-    /* handle the parts that fit into 8-byte loads/stores */
-    if ((dest + 8 <= src) || (src + 8 <= dest)) {
-        for (i = 0; i < l_64; i++) {
-            cpu_stq_data(env, dest + x, cpu_ldq_data(env, src + x));
-            x += 8;
-        }
-    }
 
     /* slow version with byte accesses which always work */
-    for (i = x; i <= l; i++) {
+    for (i = 0; i <= l; i++) {
         cpu_stb_data(env, dest + i, cpu_ldub_data(env, src + i));
     }
 }
@@ -398,11 +372,7 @@ void HELPER(mvpg)(CPUS390XState *env, uint64_t r0, uint64_t r1, uint64_t r2)
 {
     /* XXX missing r0 handling */
     env->cc_op = 0;
-#ifdef CONFIG_USER_ONLY
-    memmove(g2h(r1), g2h(r2), TARGET_PAGE_SIZE);
-#else
-    mvc_fast_memmove(env, TARGET_PAGE_SIZE, r1, r2);
-#endif
+    fast_memmove(env, r1, r2, TARGET_PAGE_SIZE);
 }
 
 /* string copy (c is string terminator) */
-- 
2.1.4