Paolo Bonzini <pbonz...@redhat.com> writes:
> On 26/04/2017 12:29, Alex Bennée wrote:
>>
>> Emilio G. Cota <c...@braap.org> writes:
>>
>>> This paves the way for upcoming work.
>>>
>>> Reviewed-by: Richard Henderson <r...@twiddle.net>
>>> Signed-off-by: Emilio G. Cota <c...@braap.org>
>>> ---
>>> tcg-runtime.c | 21 +++++++++++++++++++++
>>> tcg/tcg-runtime.h | 2 ++
>>> tcg/tcg.h | 1 +
>>> 3 files changed, 24 insertions(+)
>>>
>>> diff --git a/tcg-runtime.c b/tcg-runtime.c
>>> index 4c60c96..90d2d4b 100644
>>> --- a/tcg-runtime.c
>>> +++ b/tcg-runtime.c
>>> @@ -27,6 +27,7 @@
>>> #include "exec/helper-proto.h"
>>> #include "exec/cpu_ldst.h"
>>> #include "exec/exec-all.h"
>>> +#include "exec/tb-hash.h"
>>>
>>> /* 32-bit helpers */
>>>
>>> @@ -141,6 +142,26 @@ uint64_t HELPER(ctpop_i64)(uint64_t arg)
>>> return ctpop64(arg);
>>> }
>>>
>>> +void *HELPER(lookup_tb_ptr)(CPUArchState *env, target_ulong addr)
>>> +{
>>> + CPUState *cpu = ENV_GET_CPU(env);
>>> + TranslationBlock *tb;
>>> + target_ulong cs_base, pc;
>>> + uint32_t flags;
>>> +
>>> + if (unlikely(atomic_read(&cpu->exit_request))) {
>>> + goto out_epilogue;
>>> + }
>>> + cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
>>> + tb = atomic_rcu_read(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(addr)]);
>>> + if (likely(tb && tb->pc == addr && tb->cs_base == cs_base &&
>>> + tb->flags == flags)) {
>>
>> Should we also not be checking the TB hasn't been invalidated: tb->invalid?
>
> It's not needed because this lookup is (if I understand it right) once
> only and is not reused later. This is why tb_find doesn't check
> tb->invalid, but uses it to avoid adding the TB to the chain.
Right. And when tb->invalid = true is set we then flush it from the
jump cache so it will never be found by the helper after.
OK nothing to see here ;-)
Reviewed-by: Alex Bennée <alex.ben...@linaro.org>
>
> Good:
>
> tb_find tb_phys_invalidate
> tb_lock
> tb->invalid = true
> lookup cache
> cache hit
> tb_unlock
> tb_lock
> tb->invalid?
> yes, skip tb_add_jump
> tb_unlock
> execute tb once
>
> Bad (doesn't happen):
>
> tb_find tb_phys_invalidate
> tb_lock
> tb->invalid = true
> lookup cache
> cache hit
> tb_unlock
> tb_lock
> tb_add_jump
> tb_unlock
> execute tb many times
>
> Paolo
>
>>> + return tb->tc_ptr;
>>> + }
>>> + out_epilogue:
>>> + return tcg_ctx.code_gen_epilogue;
>>> +}
>>> +
>>> void HELPER(exit_atomic)(CPUArchState *env)
>>> {
>>> cpu_loop_exit_atomic(ENV_GET_CPU(env), GETPC());
>>> diff --git a/tcg/tcg-runtime.h b/tcg/tcg-runtime.h
>>> index 114ea6f..c41d38a 100644
>>> --- a/tcg/tcg-runtime.h
>>> +++ b/tcg/tcg-runtime.h
>>> @@ -24,6 +24,8 @@ DEF_HELPER_FLAGS_1(clrsb_i64, TCG_CALL_NO_RWG_SE, i64,
>>> i64)
>>> DEF_HELPER_FLAGS_1(ctpop_i32, TCG_CALL_NO_RWG_SE, i32, i32)
>>> DEF_HELPER_FLAGS_1(ctpop_i64, TCG_CALL_NO_RWG_SE, i64, i64)
>>>
>>> +DEF_HELPER_FLAGS_2(lookup_tb_ptr, TCG_CALL_NO_WG_SE, ptr, env, tl)
>>> +
>>> DEF_HELPER_FLAGS_1(exit_atomic, TCG_CALL_NO_WG, noreturn, env)
>>>
>>> #ifdef CONFIG_SOFTMMU
>>> diff --git a/tcg/tcg.h b/tcg/tcg.h
>>> index 6c216bb..5ec48d1 100644
>>> --- a/tcg/tcg.h
>>> +++ b/tcg/tcg.h
>>> @@ -699,6 +699,7 @@ struct TCGContext {
>>> extension that allows arithmetic on void*. */
>>> int code_gen_max_blocks;
>>> void *code_gen_prologue;
>>> + void *code_gen_epilogue;
>>> void *code_gen_buffer;
>>> size_t code_gen_buffer_size;
>>> void *code_gen_ptr;
>>
>>
>> --
>> Alex Bennée
>>
--
Alex Bennée
