tcg: Remove needless CPUState::current_tb

This field was used for telling cpu_interrupt() to unlink a chain of TBs
being executed when it worked that way. Now, cpu_interrupt() don't do
this anymore. So we don't need this field anymore.

Backports commit 3213525f8ab48742db09dab18cb9ae6f36a6c921 from qemu

qemu/cpu-exec-common.c

@@ -38,7 +38,6 @@ void cpu_resume_from_signal(CPUState *cpu, void *puc)
 
 void cpu_loop_exit(CPUState *cpu)
 {
-    cpu->current_tb = NULL;
     siglongjmp(cpu->jmp_env, 1);
 }
 
@@ -47,6 +46,5 @@ void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc)
     if (pc) {
         cpu_restore_state(cpu, pc);
     }
-    cpu->current_tb = NULL;
     siglongjmp(cpu->jmp_env, 1);
 }

qemu/cpu-exec.c

@@ -192,10 +192,8 @@ int cpu_exec(struct uc_struct *uc, CPUState *cpu)
                 }
                 if (likely(!cpu->exit_request)) {
                     uintptr_t ret;
-                    cpu->current_tb = tb;
                     /* execute the generated code */
                     ret = cpu_tb_exec(cpu, tb);
-                    cpu->current_tb = NULL;
                     last_tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
                     tb_exit = ret & TB_EXIT_MASK;
                     switch (tb_exit) {

qemu/cputlb.c

@@ -87,10 +87,6 @@ void tlb_flush(CPUState *cpu, int flush_global)
 
     tlb_debug("(%d)\n", flush_global);
 
-    /* must reset current TB so that interrupts cannot modify the
-       links while we are modifying them */
-    cpu->current_tb = NULL;
-
     memset(env->tlb_table, -1, sizeof(env->tlb_table));
     memset(env->tlb_v_table, -1, sizeof(env->tlb_v_table));
     memset(cpu->tb_jmp_cache, 0, sizeof(cpu->tb_jmp_cache));
@@ -118,9 +114,6 @@ void tlb_flush_page(CPUState *cpu, target_ulong addr)
         tlb_flush(cpu, 1);
         return;
     }
-    /* must reset current TB so that interrupts cannot modify the
-       links while we are modifying them */
-    cpu->current_tb = NULL;
 
     addr &= TARGET_PAGE_MASK;
     i = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
@@ -391,9 +384,6 @@ static inline void v_tlb_flush_by_mmuidx(CPUState *cpu, va_list argp)
     CPUArchState *env = cpu->env_ptr;
 
     tlb_debug("start\n");
-    /* must reset current TB so that interrupts cannot modify the
-       links while we are modifying them */
-    cpu->current_tb = NULL;
 
     for (;;) {
         int mmu_idx = va_arg(argp, int);
@@ -451,9 +441,6 @@ void tlb_flush_page_by_mmuidx(CPUState *cpu, target_ulong addr, ...)
         va_end(argp);
         return;
     }
-    /* must reset current TB so that interrupts cannot modify the
-       links while we are modifying them */
-    cpu->current_tb = NULL;
 
     addr &= TARGET_PAGE_MASK;
     i = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);

qemu/include/qom/cpu.h

@@ -225,7 +225,6 @@ struct CPUAddressSpace {
  * @as: Pointer to the first AddressSpace, for the convenience of targets which
  *      only have a single AddressSpace
  * @env_ptr: Pointer to subclass-specific CPUArchState field.
- * @current_tb: Currently executing TB.
  * @next_cpu: Next CPU sharing TB cache.
  * @opaque: User data.
  * @mem_io_pc: Host Program Counter at which the memory was accessed.
@@ -269,7 +268,6 @@ struct CPUState {
     MemoryRegion *memory;
 
     void *env_ptr; /* CPUArchState */
-    struct TranslationBlock *current_tb;
     struct TranslationBlock *tb_jmp_cache[TB_JMP_CACHE_SIZE];
     QTAILQ_ENTRY(CPUState) node;
 

qemu/qom/cpu.c

@@ -162,7 +162,6 @@ static void cpu_common_reset(CPUState *cpu)
     }
 
     cpu->interrupt_request = 0;
-    cpu->current_tb = NULL;
     cpu->halted = 0;
     cpu->mem_io_pc = 0;
     cpu->mem_io_vaddr = 0;

qemu/translate-all.c

@@ -297,7 +297,6 @@ bool cpu_restore_state(CPUState *cpu, uintptr_t retaddr)
         cpu_restore_state_from_tb(cpu, tb, retaddr);
         if (tb->cflags & CF_NOCACHE) {
             /* one-shot translation, invalidate it immediately */
-            cpu->current_tb = NULL;
             tb_phys_invalidate(cpu->uc, tb, -1);
             tb_free(cpu->uc, tb);
         }
@@ -1417,7 +1416,7 @@ void tb_invalidate_phys_range(struct uc_struct *uc, tb_page_addr_t start, tb_pag
 void tb_invalidate_phys_page_range(struct uc_struct *uc, tb_page_addr_t start, tb_page_addr_t end,
                                    int is_cpu_write_access)
 {
-    TranslationBlock *tb, *tb_next, *saved_tb;
+    TranslationBlock *tb, *tb_next;
     CPUState *cpu = uc->current_cpu;
 #if defined(TARGET_HAS_PRECISE_SMC)
     CPUArchState *env = NULL;
@@ -1487,20 +1486,7 @@ void tb_invalidate_phys_page_range(struct uc_struct *uc, tb_page_addr_t start, t
                                      &current_flags);
             }
 #endif /* TARGET_HAS_PRECISE_SMC */
-            /* we need to do that to handle the case where a signal
-               occurs while doing tb_phys_invalidate() */
-            saved_tb = NULL;
-            if (cpu != NULL) {
-                saved_tb = cpu->current_tb;
-                cpu->current_tb = NULL;
-            }
             tb_phys_invalidate(uc, tb, -1);
-            if (cpu != NULL) {
-                cpu->current_tb = saved_tb;
-                if (cpu->interrupt_request && cpu->current_tb) {
-                    cpu_interrupt(cpu, cpu->interrupt_request);
-                }
-            }
         }
         tb = tb_next;
     }
@@ -1516,7 +1502,6 @@ void tb_invalidate_phys_page_range(struct uc_struct *uc, tb_page_addr_t start, t
         /* we generate a block containing just the instruction
            modifying the memory. It will ensure that it cannot modify
            itself */
-        cpu->current_tb = NULL;
         tb_gen_code(cpu, current_pc, current_cs_base, current_flags, 1);
         cpu_resume_from_signal(cpu, NULL);
     }
@@ -1620,7 +1605,6 @@ static void tb_invalidate_phys_page(struct uc_struct *uc, tb_page_addr_t addr,
         /* we generate a block containing just the instruction
            modifying the memory. It will ensure that it cannot modify
            itself */
-        cpu->current_tb = NULL;
         tb_gen_code(cpu, current_pc, current_cs_base, current_flags, 1);
         if (locked) {
             mmap_unlock();