[Qemu-devel] Incoherency between the tlb and the tb_jmp_cache

[Qemu-devel] Incoherency between the tlb and the tb_jmp_cache

[Edgar E. Iglesias]

I'm seeing occational segfaults on my guest CRIS linux due to what I beleieve to be incoherency between the tlb and the tb_jmp_cache. 
This patch seems to solve the issue. Does the patch make sense or am I missing something?

Best regards
-- 
Edgar E. Iglesias
Axis Communications AB

commit 6b79550cc79e23169274236daaa8a765de0ed27f
Author: Edgar E. Iglesias <edgar.iglesias@axis.com>
Date:   Mon May 5 18:02:36 2008 +0200

    Break out tb jmp cache flushing into a separate inline function.
    Make sure to flush the jmp cache when we replace tlb entries.

diff --git a/exec.c b/exec.c
index eb3c8ab..59bca69 100644
--- a/exec.c
+++ b/exec.c
@@ -1366,6 +1366,21 @@ CPUState *cpu_copy(CPUState *env)
 
 #if !defined(CONFIG_USER_ONLY)
 
+static inline void tlb_flush_jmp_cache(CPUState *env, target_ulong addr)
+{
+    unsigned int i;
+
+    /* Discard jump cache entries for any tb which might potentially
+       overlap the flushed page.  */
+    i = tb_jmp_cache_hash_page(addr - TARGET_PAGE_SIZE);
+    memset (&env->tb_jmp_cache[i], 0, 
+	    TB_JMP_PAGE_SIZE * sizeof(TranslationBlock *));
+
+    i = tb_jmp_cache_hash_page(addr);
+    memset (&env->tb_jmp_cache[i], 0, 
+	    TB_JMP_PAGE_SIZE * sizeof(TranslationBlock *));
+}
+
 /* NOTE: if flush_global is true, also flush global entries (not
    implemented yet) */
 void tlb_flush(CPUState *env, int flush_global)
@@ -1428,7 +1443,6 @@ static inline void tlb_flush_entry(CPUTLBEntry *tlb_entry, target_ulong addr)
 void tlb_flush_page(CPUState *env, target_ulong addr)
 {
     int i;
-    TranslationBlock *tb;
 
 #if defined(DEBUG_TLB)
     printf("tlb_flush_page: " TARGET_FMT_lx "\n", addr);
@@ -1448,13 +1462,7 @@ void tlb_flush_page(CPUState *env, target_ulong addr)
 #endif
 #endif
 
-    /* Discard jump cache entries for any tb which might potentially
-       overlap the flushed page.  */
-    i = tb_jmp_cache_hash_page(addr - TARGET_PAGE_SIZE);
-    memset (&env->tb_jmp_cache[i], 0, TB_JMP_PAGE_SIZE * sizeof(tb));
-
-    i = tb_jmp_cache_hash_page(addr);
-    memset (&env->tb_jmp_cache[i], 0, TB_JMP_PAGE_SIZE * sizeof(tb));
+    tlb_flush_jmp_cache(env, addr);
 
 #if !defined(CONFIG_SOFTMMU)
     if (addr < MMAP_AREA_END)
@@ -1706,6 +1714,10 @@ int tlb_set_page_exec(CPUState *env, target_ulong vaddr,
         } else {
             te->addr_read = -1;
         }
+
+        if (te->addr_code != -1) {
+            tlb_flush_jmp_cache(env, te->addr_code);
+        }
         if (prot & PAGE_EXEC) {
             te->addr_code = address;
         } else {