Having this data in cflags means that hashing takes care of selecting a TB with or without exceptions built in. Which means that we no longer need to flush all TBs.
This does require that we single-step while we're within a page that contains a breakpoint, so it's not yet ideal, but should be an improvement over some corner-case slowdowns. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/404 Signed-off-by: Richard Henderson <richard.hender...@linaro.org> --- include/exec/exec-all.h | 7 ++++ accel/tcg/cpu-exec.c | 68 ++++++++++++++++++++++++++++++- accel/tcg/translate-all.c | 4 -- accel/tcg/translator.c | 85 +++++++++++++++++++++------------------ cpu.c | 24 ----------- 5 files changed, 119 insertions(+), 69 deletions(-) diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index 6873cce8df..7ab2578f71 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -502,9 +502,16 @@ struct TranslationBlock { #define CF_USE_ICOUNT 0x00020000 #define CF_INVALID 0x00040000 /* TB is stale. Set with @jmp_lock held */ #define CF_PARALLEL 0x00080000 /* Generate code for a parallel context */ +#define CF_BP_MASK 0x00300000 /* See below */ +#define CF_BP_SHIFT 20 #define CF_CLUSTER_MASK 0xff000000 /* Top 8 bits are cluster ID */ #define CF_CLUSTER_SHIFT 24 +#define CF_BP_NONE (0 << CF_BP_SHIFT) /* TB does not interact with BPs */ +#define CF_BP_SSTEP (1 << CF_BP_SHIFT) /* gdbstub single-step in effect */ +#define CF_BP_GDB (2 << CF_BP_SHIFT) /* gdbstub breakpoint at tb->pc */ +#define CF_BP_CPU (3 << CF_BP_SHIFT) /* arch breakpoint at tb->pc */ + /* Per-vCPU dynamic tracing state used to generate this TB */ uint32_t trace_vcpu_dstate; diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index 4d043a11aa..179a425ece 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -222,6 +222,65 @@ static inline void log_cpu_exec(target_ulong pc, CPUState *cpu, } } +static uint32_t cflags_for_breakpoints(CPUState *cpu, target_ulong pc, + uint32_t cflags) +{ + uint32_t bflags = 0; + + if (unlikely(cpu->singlestep_enabled)) { + bflags = CF_BP_SSTEP; + } else { + bool match_page = false; + CPUBreakpoint *bp; + + QTAILQ_FOREACH(bp, &cpu->breakpoints, entry) { + /* Note exact pc matches */ + if (pc == bp->pc) { + if (bp->flags & BP_GDB) { + bflags = CF_BP_GDB; + break; + } + if (bp->flags & BP_CPU) { + bflags = CF_BP_CPU; + break; + } + } + /* Note page matches */ + if (((pc ^ bp->pc) & TARGET_PAGE_MASK) == 0) { + match_page = true; + } + } + + if (likely(!bflags)) { + if (likely(!match_page)) { + return cflags; + } + + /* + * Within the same page as a breakpoint, single-step, + * returning to helper_lookup_tb_ptr after each looking + * for the actual breakpoint. + * + * TODO: Perhaps better to record all of the TBs associated + * with a given virtual page that contains a breakpoint, and + * then invalidate them when a new overlapping breakpoint is + * set on the page. Non-overlapping TBs would not be + * invalidated, nor would any TB need to be invalidated as + * breakpoints are removed. + */ + bflags = CF_NO_GOTO_TB; + } + } + + /* + * Reduce the TB to one insn. + * In the case of a BP hit, we will be raising an exception anyway. + * In the case of a page hit, return to helper_lookup_tb_ptr after + * every insn to look for the breakpoint. + */ + return (cflags & ~CF_COUNT_MASK) | 1 | bflags; +} + /** * helper_lookup_tb_ptr: quick check for next tb * @env: current cpu state @@ -235,11 +294,13 @@ const void *HELPER(lookup_tb_ptr)(CPUArchState *env) CPUState *cpu = env_cpu(env); TranslationBlock *tb; target_ulong cs_base, pc; - uint32_t flags; + uint32_t flags, cflags; cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags); - tb = tb_lookup(cpu, pc, cs_base, flags, curr_cflags(cpu)); + cflags = cflags_for_breakpoints(cpu, pc, curr_cflags(cpu)); + + tb = tb_lookup(cpu, pc, cs_base, flags, cflags); if (tb == NULL) { return tcg_code_gen_epilogue; } @@ -346,6 +407,8 @@ void cpu_exec_step_atomic(CPUState *cpu) cflags &= ~CF_PARALLEL; /* After 1 insn, return and release the exclusive lock. */ cflags |= CF_NO_GOTO_TB | CF_NO_GOTO_PTR | 1; + /* Raise any post-instruction debug exceptions. */ + cflags = cflags_for_breakpoints(cpu, pc, cflags); tb = tb_lookup(cpu, pc, cs_base, flags, cflags); if (tb == NULL) { @@ -524,6 +587,7 @@ static inline TranslationBlock *tb_find(CPUState *cpu, } else { cpu->cflags_next_tb = -1; } + cflags = cflags_for_breakpoints(cpu, pc, cflags); tb = tb_lookup(cpu, pc, cs_base, flags, cflags); if (tb == NULL) { diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c index bf82c15aab..bbfcfb698c 100644 --- a/accel/tcg/translate-all.c +++ b/accel/tcg/translate-all.c @@ -1432,10 +1432,6 @@ TranslationBlock *tb_gen_code(CPUState *cpu, } QEMU_BUILD_BUG_ON(CF_COUNT_MASK + 1 != TCG_MAX_INSNS); - if (cpu->singlestep_enabled) { - max_insns = 1; - } - buffer_overflow: tb = tcg_tb_alloc(tcg_ctx); if (unlikely(!tb)) { diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c index 449159a27c..01b48137da 100644 --- a/accel/tcg/translator.c +++ b/accel/tcg/translator.c @@ -33,13 +33,8 @@ void translator_loop_temp_check(DisasContextBase *db) bool translator_use_goto_tb(DisasContextBase *db, target_ulong dest) { - /* Suppress goto_tb if requested. */ - if (tb_cflags(db->tb) & CF_NO_GOTO_TB) { - return false; - } - - /* Suppress goto_tb in the case of single-steping. */ - if (db->singlestep_enabled) { + /* Suppress goto_tb if requested, or required by breakpoints. */ + if (tb_cflags(db->tb) & (CF_NO_GOTO_TB | CF_BP_MASK)) { return false; } @@ -51,6 +46,7 @@ void translator_loop(const TranslatorOps *ops, DisasContextBase *db, CPUState *cpu, TranslationBlock *tb, int max_insns) { uint32_t cflags = tb_cflags(tb); + int bp_flags = 0; bool plugin_enabled; /* Initialize DisasContext */ @@ -60,7 +56,23 @@ void translator_loop(const TranslatorOps *ops, DisasContextBase *db, db->is_jmp = DISAS_NEXT; db->num_insns = 0; db->max_insns = max_insns; - db->singlestep_enabled = cpu->singlestep_enabled; + db->singlestep_enabled = false; + + switch (cflags & CF_BP_MASK) { + case CF_BP_NONE: + break; + case CF_BP_SSTEP: + db->singlestep_enabled = true; + break; + case CF_BP_GDB: + bp_flags = BP_GDB; + break; + case CF_BP_CPU: + bp_flags = BP_CPU; + break; + default: + g_assert_not_reached(); + } ops->init_disas_context(db, cpu); tcg_debug_assert(db->is_jmp == DISAS_NEXT); /* no early exit */ @@ -85,39 +97,34 @@ void translator_loop(const TranslatorOps *ops, DisasContextBase *db, } /* Pass breakpoint hits to target for further processing */ - if (!db->singlestep_enabled - && unlikely(!QTAILQ_EMPTY(&cpu->breakpoints))) { - CPUBreakpoint *bp; - QTAILQ_FOREACH(bp, &cpu->breakpoints, entry) { - if (bp->pc == db->pc_next) { - int len = ops->breakpoint_check(db, cpu, bp->flags); + if (unlikely(bp_flags)) { + int len = ops->breakpoint_check(db, cpu, bp_flags); - /* - * The breakpoint_check hook may use DISAS_TOO_MANY - * to indicate that only one more instruction is to - * be executed. Otherwise it should use DISAS_NORETURN - * when generating an exception, but may use a - * DISAS_TARGET_* value for Something Else. - */ - if (db->is_jmp > DISAS_TOO_MANY) { - /* - * The address covered by the breakpoint must be - * included in [tb->pc, tb->pc + tb->size) in order - * to for it to be properly cleared. Thus we - * increment the PC here so that the logic setting - * tb->size below does the right thing. - */ - tcg_debug_assert(len > 0); - db->pc_next += len; + /* + * When there is a bp hit, we're going to execute a maximum + * of one instruction. The breakpoint_check hook may use + * DISAS_NEXT or DISAS_TOO_MANY to indicate that the current + * instruction should be translated. Anything else is taken + * to mean that an exception has been raised and that zero + * instructions will be executed. + */ + if (db->is_jmp > DISAS_TOO_MANY) { + /* + * The address covered by the breakpoint must be + * included in [tb->pc, tb->pc + tb->size) in order + * to for it to be properly cleared. Thus we + * increment the PC here so that the logic setting + * tb->size below does the right thing. + */ + tcg_debug_assert(len > 0); + db->pc_next += len; - /* - * The breakpoint definitely hit, so decrement the - * number of instructions completed for icount. - */ - db->num_insns--; - goto done; - } - } + /* + * The breakpoint definitely hit, so decrement the + * number of instructions completed for icount. + */ + db->num_insns--; + goto done; } } diff --git a/cpu.c b/cpu.c index 83059537d7..addcb5db9c 100644 --- a/cpu.c +++ b/cpu.c @@ -225,11 +225,6 @@ void tb_invalidate_phys_addr(target_ulong addr) tb_invalidate_phys_page_range(addr, addr + 1); mmap_unlock(); } - -static void breakpoint_invalidate(CPUState *cpu, target_ulong pc) -{ - tb_invalidate_phys_addr(pc); -} #else void tb_invalidate_phys_addr(AddressSpace *as, hwaddr addr, MemTxAttrs attrs) { @@ -250,17 +245,6 @@ void tb_invalidate_phys_addr(AddressSpace *as, hwaddr addr, MemTxAttrs attrs) ram_addr = memory_region_get_ram_addr(mr) + addr; tb_invalidate_phys_page_range(ram_addr, ram_addr + 1); } - -static void breakpoint_invalidate(CPUState *cpu, target_ulong pc) -{ - /* - * There may not be a virtual to physical translation for the pc - * right now, but there may exist cached TB for this pc. - * Flush the whole TB cache to force re-translation of such TBs. - * This is heavyweight, but we're debugging anyway. - */ - tb_flush(cpu); -} #endif /* Add a breakpoint. */ @@ -281,8 +265,6 @@ int cpu_breakpoint_insert(CPUState *cpu, vaddr pc, int flags, QTAILQ_INSERT_TAIL(&cpu->breakpoints, bp, entry); } - breakpoint_invalidate(cpu, pc); - if (breakpoint) { *breakpoint = bp; } @@ -310,8 +292,6 @@ void cpu_breakpoint_remove_by_ref(CPUState *cpu, CPUBreakpoint *bp) { QTAILQ_REMOVE(&cpu->breakpoints, bp, entry); - breakpoint_invalidate(cpu, bp->pc); - trace_breakpoint_remove(cpu->cpu_index, bp->pc, bp->flags); g_free(bp); } @@ -336,10 +316,6 @@ void cpu_single_step(CPUState *cpu, int enabled) cpu->singlestep_enabled = enabled; if (kvm_enabled()) { kvm_update_guest_debug(cpu, 0); - } else { - /* must flush all the translated code to avoid inconsistencies */ - /* XXX: only flush what is necessary */ - tb_flush(cpu); } trace_breakpoint_singlestep(cpu->cpu_index, enabled); } -- 2.25.1