Re: [Xen-devel] [PATCH v4 01/39] arm/p2m: Introduce p2m_(switch|restore)_vttbr_and_(g|s)et_flags

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

Hi Julien,

please excuse me for the long delay.

On 10/09/2017 06:25 PM, Julien Grall wrote:
> Hi Sergej,
>
> On 30/08/17 19:32, Sergej Proskurin wrote:
>> This commit introduces macros for switching and restoring the vttbr
>> considering the currently set irq flags. We define these macros, as the
>> following commits will use the associated functionality multiple times
>> throughout different files.
>>
>> Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
>> ---
>> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>> Cc: Julien Grall <julien.grall@xxxxxxx>
>> ---
>> v4: Save the content of VTTBR_EL2 inside of the introduced macro
>>      "p2m_switch_vttbr_and_get_flags".
>>
>>      Move the introduced macros into ./xen/include/asm-arm/p2m.h, as
>> they will
>>      be used by different files in the future commits.
>
> I don't like the idea of moving such macros in p2m.h because it expose
> the underlying implementation of P2M.
>
> A better solution would be introduce a helper to translate from a
> guest VA to guest PA in p2m.c. This helper will switch to the host P2M
> if necessary.

I agree, thank you. This would eliminate the unnecessary macro
invocations in mem_access.c. I will include such wrapper in p2m.c in the
next version of the altp2m patch series.

Do you think it would make sense to submit the upper macros for saving
and restoring the VTTBR and flags as a standalone patch in form of a
cosmetic fix? This would simplify the function p2m_force_tlb_flush_sync
in p2m.c.

Thanks,
~Sergej


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