[Qemu-devel] [RFC PATCH v4 11/25] cpu-exec: allow temporary disabling icount

[Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>]

This patch is required for deterministic replay to generate an exception
by trying executing an instruction without changing icount.
It adds new flag to TB for disabling icount while translating it.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
---
 cpu-exec.c              |    6 +++---
 include/exec/exec-all.h |    7 ++++---
 translate-all.c         |   22 ++++++++++++++++++++--
 3 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/cpu-exec.c b/cpu-exec.c
index 011f51f..e7206ac 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -198,7 +198,7 @@ static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, uint8_t *tb_ptr)
 /* Execute the code without caching the generated code. An interpreter
    could be used if available. */
 static void cpu_exec_nocache(CPUArchState *env, int max_cycles,
-                             TranslationBlock *orig_tb)
+                             TranslationBlock *orig_tb, bool ignore_icount)
 {
     CPUState *cpu = ENV_GET_CPU(env);
     TranslationBlock *tb;
@@ -214,7 +214,7 @@ static void cpu_exec_nocache(CPUArchState *env, int max_cycles,
     /* tb_gen_code can flush our orig_tb, invalidate it now */
     tb_phys_invalidate(orig_tb, -1);
     tb = tb_gen_code(cpu, pc, cs_base, flags,
-                     max_cycles);
+                     max_cycles | (ignore_icount ? CF_IGNORE_ICOUNT : 0));
     cpu->current_tb = tb;
     /* execute the generated code */
     trace_exec_tb_nocache(tb, tb->pc);
@@ -516,7 +516,7 @@ int cpu_exec(CPUArchState *env)
                         } else {
                             if (insns_left > 0) {
                                 /* Execute remaining instructions.  */
-                                cpu_exec_nocache(env, insns_left, tb);
+                                cpu_exec_nocache(env, insns_left, tb, false);
                                 align_clocks(&sc, cpu);
                             }
                             cpu->exception_index = EXCP_INTERRUPT;
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 1d17f75..052e8ef 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -142,9 +142,10 @@ struct TranslationBlock {
     uint64_t flags; /* flags defining in which context the code was generated */
     uint16_t size;      /* size of target code for this block (1 <=
                            size <= TARGET_PAGE_SIZE) */
-    uint16_t cflags;    /* compile flags */
-#define CF_COUNT_MASK  0x7fff
-#define CF_LAST_IO     0x8000 /* Last insn may be an IO access.  */
+    uint32_t cflags;    /* compile flags */
+#define CF_COUNT_MASK    0x7fff
+#define CF_LAST_IO       0x8000 /* Last insn may be an IO access.  */
+#define CF_IGNORE_ICOUNT 0x10000 /* Do not generate icount code */
 
     void *tc_ptr;    /* pointer to the translated code */
     /* next matching tb for physical address. */
diff --git a/translate-all.c b/translate-all.c
index 7177b71..182ea7d 100644
--- a/translate-all.c
+++ b/translate-all.c
@@ -207,6 +207,7 @@ static int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
     TCGContext *s = &tcg_ctx;
     int j;
     uintptr_t tc_ptr;
+    int old_icount = use_icount;
 #ifdef CONFIG_PROFILER
     int64_t ti;
 #endif
@@ -218,6 +219,10 @@ static int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
 
     gen_intermediate_code_pc(env, tb);
 
+    if (tb->cflags & CF_IGNORE_ICOUNT) {
+        use_icount = 0;
+    }
+
     if (use_icount) {
         /* Reset the cycle counter to the start of the block.  */
         cpu->icount_decr.u16.low += tb->icount;
@@ -227,8 +232,10 @@ static int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
 
     /* find opc index corresponding to search_pc */
     tc_ptr = (uintptr_t)tb->tc_ptr;
-    if (searched_pc < tc_ptr)
+    if (searched_pc < tc_ptr) {
+        use_icount = old_icount;
         return -1;
+    }
 
     s->tb_next_offset = tb->tb_next_offset;
 #ifdef USE_DIRECT_JUMP
@@ -240,8 +247,10 @@ static int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
 #endif
     j = tcg_gen_code_search_pc(s, (tcg_insn_unit *)tc_ptr,
                                searched_pc - tc_ptr);
-    if (j < 0)
+    if (j < 0) {
+        use_icount = old_icount;
         return -1;
+    }
     /* now find start of instruction before */
     while (s->gen_opc_instr_start[j] == 0) {
         j--;
@@ -254,6 +263,8 @@ static int cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
     s->restore_time += profile_getclock() - ti;
     s->restore_count++;
 #endif
+    use_icount = old_icount;
+
     return 0;
 }
 
@@ -264,6 +275,8 @@ bool cpu_restore_state(CPUState *cpu, uintptr_t retaddr)
     tb = tb_find_pc(retaddr);
     if (tb) {
         cpu_restore_state_from_tb(cpu, tb, retaddr);
+        /* tb could be temporary, generated by exec nocache */
+        tb_phys_invalidate(tb, -1);
         return true;
     }
     return false;
@@ -1045,6 +1058,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
     tb_page_addr_t phys_pc, phys_page2;
     target_ulong virt_page2;
     int code_gen_size;
+    int old_icount = use_icount;
 
     phys_pc = get_page_addr_code(env, pc);
     tb = tb_alloc(pc);
@@ -1060,9 +1074,13 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
     tb->cs_base = cs_base;
     tb->flags = flags;
     tb->cflags = cflags;
+    if (cflags & CF_IGNORE_ICOUNT) {
+        use_icount = 0;
+    }
     cpu_gen_code(env, tb, &code_gen_size);
     tcg_ctx.code_gen_ptr = (void *)(((uintptr_t)tcg_ctx.code_gen_ptr +
             code_gen_size + CODE_GEN_ALIGN - 1) & ~(CODE_GEN_ALIGN - 1));
+    use_icount = old_icount;
 
     /* check next page if needed */
     virt_page2 = (pc + tb->size - 1) & TARGET_PAGE_MASK;