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Re: [PATCH v11 18/25] cpu: Move synchronize_from_tb() to tcg_ops


From: Claudio Fontana
Subject: Re: [PATCH v11 18/25] cpu: Move synchronize_from_tb() to tcg_ops
Date: Fri, 11 Dec 2020 18:47:34 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0

On 12/11/20 6:28 PM, Richard Henderson wrote:
> On 12/11/20 11:10 AM, Claudio Fontana wrote:
>> On 12/11/20 6:05 PM, Richard Henderson wrote:
>>> On 12/11/20 2:31 AM, Claudio Fontana wrote:
>>>> From: Eduardo Habkost <ehabkost@redhat.com>
>>>>
>>>> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>>>> [claudio: wrapped in CONFIG_TCG]
>>>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
>>>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>>> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
>>>> ---
>>>>  include/hw/core/cpu.h         |  8 --------
>>>>  include/hw/core/tcg-cpu-ops.h | 12 ++++++++++++
>>>>  accel/tcg/cpu-exec.c          |  4 ++--
>>>>  target/arm/cpu.c              |  4 +++-
>>>>  target/avr/cpu.c              |  2 +-
>>>>  target/hppa/cpu.c             |  2 +-
>>>>  target/i386/tcg/tcg-cpu.c     |  2 +-
>>>>  target/microblaze/cpu.c       |  2 +-
>>>>  target/mips/cpu.c             |  4 +++-
>>>>  target/riscv/cpu.c            |  2 +-
>>>>  target/rx/cpu.c               |  2 +-
>>>>  target/sh4/cpu.c              |  2 +-
>>>>  target/sparc/cpu.c            |  2 +-
>>>>  target/tricore/cpu.c          |  2 +-
>>>>  14 files changed, 29 insertions(+), 21 deletions(-)
>>>>
>>>> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
>>>> index ea648d52ad..83007d262c 100644
>>>> --- a/include/hw/core/cpu.h
>>>> +++ b/include/hw/core/cpu.h
>>>> @@ -110,13 +110,6 @@ struct TranslationBlock;
>>>>   *       If the target behaviour here is anything other than "set
>>>>   *       the PC register to the value passed in" then the target must
>>>>   *       also implement the synchronize_from_tb hook.
>>>> - * @synchronize_from_tb: Callback for synchronizing state from a TCG
>>>> - *       #TranslationBlock. This is called when we abandon execution
>>>> - *       of a TB before starting it, and must set all parts of the CPU
>>>> - *       state which the previous TB in the chain may not have updated.
>>>> - *       This always includes at least the program counter; some targets
>>>> - *       will need to do more. If this hook is not implemented then the
>>>> - *       default is to call @set_pc(tb->pc).
>>>>   * @tlb_fill: Callback for handling a softmmu tlb miss or user-only
>>>>   *       address fault.  For system mode, if the access is valid, call
>>>>   *       tlb_set_page and return true; if the access is invalid, and
>>>> @@ -193,7 +186,6 @@ struct CPUClass {
>>>>      void (*get_memory_mapping)(CPUState *cpu, MemoryMappingList *list,
>>>>                                 Error **errp);
>>>>      void (*set_pc)(CPUState *cpu, vaddr value);
>>>> -    void (*synchronize_from_tb)(CPUState *cpu, struct TranslationBlock 
>>>> *tb);
>>>>      bool (*tlb_fill)(CPUState *cpu, vaddr address, int size,
>>>>                       MMUAccessType access_type, int mmu_idx,
>>>>                       bool probe, uintptr_t retaddr);
>>>> diff --git a/include/hw/core/tcg-cpu-ops.h b/include/hw/core/tcg-cpu-ops.h
>>>> index 4475ef0996..e1d50b3c8b 100644
>>>> --- a/include/hw/core/tcg-cpu-ops.h
>>>> +++ b/include/hw/core/tcg-cpu-ops.h
>>>> @@ -10,6 +10,8 @@
>>>>  #ifndef TCG_CPU_OPS_H
>>>>  #define TCG_CPU_OPS_H
>>>>  
>>>> +#include "hw/core/cpu.h"
>>>
>>> This include is circular.
>>
>> Yes, it's protected though, it was asked that way.
> 
> Well, in my strong opinion, someone asked incorrectly.  It's "harmless" 
> because
> of the protection ifdefs, but it's Wrong because it has the potential to hide 
> bugs.
> 
> What is it that you thought you needed from core/cpu.h anyway?
> 
>>> Are you sure that splitting out hw/core/tcg-cpu-ops.h from hw/core/cpu.h in
>>> patch 15 is even useful?
>>
>> it avoids a huge #ifdef CONFIG_TCG
> 
> So?  The question should be: is it useful on its own, and I think the answer 
> to
> that is clearly not.  Thus it should not pretend to be a standalone header 
> file.
> 
> 
> r~
> 

The whole point of the exercise is to sort out what is tcg specific and only 
compile it under CONFIG_TCG.

Having everything inside cpu.h wrapped in a 100 line #ifdef is not particularly 
readable or discoverable,
so I think it is actually useful for understanding purposes to have it separate,
but that said, I don't feel strongly on this, as I intend to improve this in 
later series.

Thanks,

Claudio


















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