Re: [RFC v18 08/15] i386: split smm helper (softmmu)

[Claudio Fontana <cfontana@suse.de>]

On 2/15/21 1:32 PM, Alex Bennée wrote:
> 
> Claudio Fontana <cfontana@suse.de> writes:
> 
>> On 2/12/21 1:36 PM, Claudio Fontana wrote:
>>> smm is only really useful for softmmu, split in two modules
>>> around the CONFIG_USER_ONLY, in order to remove the ifdef
>>> and use the build system instead.
>>>
>>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
>>> ---
>>>  target/i386/helper.h                       |  4 ++++
>>>  target/i386/tcg/seg_helper.c               |  2 ++
>>>  target/i386/tcg/{ => softmmu}/smm_helper.c | 19 ++-----------------
>>>  target/i386/tcg/translate.c                |  2 ++
>>>  target/i386/tcg/meson.build                |  1 -
>>>  target/i386/tcg/softmmu/meson.build        |  1 +
>>>  6 files changed, 11 insertions(+), 18 deletions(-)
>>>  rename target/i386/tcg/{ => softmmu}/smm_helper.c (98%)
>>>
>>> diff --git a/target/i386/helper.h b/target/i386/helper.h
>>> index c2ae2f7e61..8ffda4cdc6 100644
>>> --- a/target/i386/helper.h
>>> +++ b/target/i386/helper.h
>>> @@ -70,7 +70,11 @@ DEF_HELPER_1(clac, void, env)
>>>  DEF_HELPER_1(stac, void, env)
>>>  DEF_HELPER_3(boundw, void, env, tl, int)
>>>  DEF_HELPER_3(boundl, void, env, tl, int)
>>> +
>>> +#ifndef CONFIG_USER_ONLY
>>>  DEF_HELPER_1(rsm, void, env)
>>> +#endif /* !CONFIG_USER_ONLY */
>>> +
>>>  DEF_HELPER_2(into, void, env, int)
>>>  DEF_HELPER_2(cmpxchg8b_unlocked, void, env, tl)
>>>  DEF_HELPER_2(cmpxchg8b, void, env, tl)
>>> diff --git a/target/i386/tcg/seg_helper.c b/target/i386/tcg/seg_helper.c
>>> index 180d47f0e9..f0cb1bffe7 100644
>>> --- a/target/i386/tcg/seg_helper.c
>>> +++ b/target/i386/tcg/seg_helper.c
>>> @@ -1351,7 +1351,9 @@ bool x86_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
>>>      case CPU_INTERRUPT_SMI:
>>>          cpu_svm_check_intercept_param(env, SVM_EXIT_SMI, 0, 0);
>>>          cs->interrupt_request &= ~CPU_INTERRUPT_SMI;
>>> +#ifndef CONFIG_USER_ONLY
>>>          do_smm_enter(cpu);
>>> +#endif
>>>          break;
>>>      case CPU_INTERRUPT_NMI:
>>>          cpu_svm_check_intercept_param(env, SVM_EXIT_NMI, 0, 0);
>>> diff --git a/target/i386/tcg/smm_helper.c b/target/i386/tcg/softmmu/smm_helper.c
>>> similarity index 98%
>>> rename from target/i386/tcg/smm_helper.c
>>> rename to target/i386/tcg/softmmu/smm_helper.c
>>> index 62d027abd3..ee53b26629 100644
>>> --- a/target/i386/tcg/smm_helper.c
>>> +++ b/target/i386/tcg/softmmu/smm_helper.c
>>> @@ -1,5 +1,5 @@
>>>  /*
>>> - *  x86 SMM helpers
>>> + *  x86 SMM helpers (softmmu-only)
>>>   *
>>>   *  Copyright (c) 2003 Fabrice Bellard
>>>   *
>>> @@ -18,27 +18,14 @@
>>>   */
>>>  
>>>  #include "qemu/osdep.h"
>>> -#include "qemu/main-loop.h"
>>>  #include "cpu.h"
>>>  #include "exec/helper-proto.h"
>>>  #include "exec/log.h"
>>> -#include "helper-tcg.h"
>>> +#include "tcg/helper-tcg.h"
>>>  
>>>  
>>>  /* SMM support */
>>>  
>>> -#if defined(CONFIG_USER_ONLY)
>>> -
>>> -void do_smm_enter(X86CPU *cpu)
>>> -{
>>> -}
>>> -
>>> -void helper_rsm(CPUX86State *env)
>>> -{
>>> -}
>>> -
>>> -#else
>>> -
>>>  #ifdef TARGET_X86_64
>>>  #define SMM_REVISION_ID 0x00020064
>>>  #else
>>> @@ -330,5 +317,3 @@ void helper_rsm(CPUX86State *env)
>>>      qemu_log_mask(CPU_LOG_INT, "SMM: after RSM\n");
>>>      log_cpu_state_mask(CPU_LOG_INT, CPU(cpu), CPU_DUMP_CCOP);
>>>  }
>>> -
>>> -#endif /* !CONFIG_USER_ONLY */
>>> diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c
>>> index af1faf9342..5075ac4830 100644
>>> --- a/target/i386/tcg/translate.c
>>> +++ b/target/i386/tcg/translate.c
>>> @@ -8321,7 +8321,9 @@ static target_ulong disas_insn(DisasContext *s, CPUState *cpu)
>>>              goto illegal_op;
>>>          gen_update_cc_op(s);
>>>          gen_jmp_im(s, s->pc - s->cs_base);
>>> +#ifndef CONFIG_USER_ONLY
>>>          gen_helper_rsm(cpu_env);
>>> +#endif /* CONFIG_USER_ONLY */
>>>          gen_eob(s);
>>>          break;
>>
>> Hello Alex,
>>
>> this is something I wanted to bring in the foreground:
>>
>> while before we were generating an empty helper call for CONFIG_USER_ONLY,
>> now we are not generating anything.
> 
> Surely that says we only generate the helper call when we are not
> CONFIG_USER_ONLY?

Yes. The difference between before the patch and after the patch
is that before we were still going through all the code in tcg_gen_callN,
via the call to gen_helper_rsm macro, only to call finally an empty function for CONFIG_USER_ONLY (helper_rsm() {}),

while now we do not generate anything, we do not call the gen_helper_rsm macro at all, so we don't go through tcg_gen_callN.

> 
> 
>>
>>
>>
>>>      case 0x1b8: /* SSE4.2 popcnt */
>>> diff --git a/target/i386/tcg/meson.build b/target/i386/tcg/meson.build
>>> index 68fa0c3187..ec5daa1edc 100644
>>> --- a/target/i386/tcg/meson.build
>>> +++ b/target/i386/tcg/meson.build
>>> @@ -8,7 +8,6 @@ i386_ss.add(when: 'CONFIG_TCG', if_true: files(
>>>    'misc_helper.c',
>>>    'mpx_helper.c',
>>>    'seg_helper.c',
>>> -  'smm_helper.c',
>>>    'svm_helper.c',
>>>    'tcg-cpu.c',
>>>    'translate.c'), if_false: files('tcg-stub.c'))
>>> diff --git a/target/i386/tcg/softmmu/meson.build b/target/i386/tcg/softmmu/meson.build
>>> index 4ab30cc32e..35ba16dc3d 100644
>>> --- a/target/i386/tcg/softmmu/meson.build
>>> +++ b/target/i386/tcg/softmmu/meson.build
>>> @@ -1,3 +1,4 @@
>>>  i386_softmmu_ss.add(when: ['CONFIG_TCG', 'CONFIG_SOFTMMU'], if_true: files(
>>>    'tcg-cpu.c',
>>> +  'smm_helper.c',
>>>  ))
>>>
> 
>