Re: [RFC PATCH V1 08/12] xen/arm: Invalidate qemu mapcache on XENMEM_decrease_reservation

[Jan Beulich <jbeulich@xxxxxxxx>]

On 06.08.2020 16:28, Oleksandr wrote:
> 
> On 06.08.20 14:50, Jan Beulich wrote:
> 
> Hi Jan
> 
>>>> On 03.08.2020 20:21, Oleksandr Tyshchenko wrote:
>>>>> --- a/xen/common/memory.c
>>>>> +++ b/xen/common/memory.c
>>>>> @@ -1652,6 +1652,12 @@ long do_memory_op(unsigned long cmd, 
>>>>> XEN_GUEST_HANDLE_PARAM(void) arg)
>>>>>            break;
>>>>>        }
>>>>>    
>>>>> +    /* x86 already sets the flag in hvm_memory_op() */
>>>>> +#if defined(CONFIG_ARM64) && defined(CONFIG_IOREQ_SERVER)
>>>>> +    if ( op == XENMEM_decrease_reservation )
>>>>> +        curr_d->arch.hvm.qemu_mapcache_invalidate = true;
>>>>> +#endif
>>>> Doesn't the comment already indicate a route towards an approach
>>>> not requiring to alter common code?
>>> Given that IOREQ is now moved under common/, I think it would make sense
>>> to have this set in common code as well for all the architecture.
>>>
>>> IOW, I would suggest to drop the #ifdef CONFIG_ARM64. In addition, we
>>> may want to introduce an helper to check if a domain is using ioreq.
>> Of course, with the (part of the) conditional dropped and the struct
>> field moved out of the arch sub-struct, this is fine to live here.
> 
> ok.
> 
> 
> I suspect this should *also* live in compat_memory_op(). Please confirm 
> whether my understanding correct.

Doesn't compat_memory_op() simply call here, so will have the flag set
as needed?

Jan