Re: [RFC PATCH-for-10.1 3/4] tcg: Have tcg_req_mo() use runtime TCGContext::guest_mo

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 21/3/25 15:39, Anton Johansson wrote:
> On 21/03/25, Philippe Mathieu-Daudé wrote:
>> In order to use TCG with multiple targets, replace the
>> compile time use of TCG_GUEST_DEFAULT_MO by a runtime
>> access to tcg_ctx->guest_mo.
>>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> ---
>>   accel/tcg/internal-target.h | 4 +---
>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/accel/tcg/internal-target.h b/accel/tcg/internal-target.h
>> index 1cb35dba99e..014ee756f9d 100644
>> --- a/accel/tcg/internal-target.h
>> +++ b/accel/tcg/internal-target.h
>> @@ -49,11 +49,9 @@ G_NORETURN void cpu_io_recompile(CPUState *cpu, uintptr_t retaddr);
>>    * Filter @type to the barrier that is required for the guest
>>    * memory ordering vs the host memory ordering.  A non-zero
>>    * result indicates that some barrier is required.
>> - *
>> - * This is a macro so that it's constant even without optimization.
>>    */
>>   #define tcg_req_mo(type) \
>> -    ((type) & TCG_GUEST_DEFAULT_MO & ~TCG_TARGET_DEFAULT_MO)
>> +    ((type) & tcg_ctx->guest_mo & ~TCG_TARGET_DEFAULT_MO)
>>   
>>   /**
>>    * cpu_req_mo:
>> -- 
>> 2.47.1
>>
> 
> I'll parrot some older feedback by Richard
> 
>    https://lore.kernel.org/all/92cc9335-10bf-4a74-9eb4-249de5545dc5@linaro.org/
> 
> but tcg_ctx->guest_mo can be undefined or bogus here. Could we not
> take cpu and access cpu->cc->tcg_ops->guest_default_memory_order
> directly instead?

Yes, cpu_req_mo() has access to @cpu.