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Re: [Xen-devel] [PATCH v1 08/10] iommu: Split iommu_hwdom_init() into arch specific parts

Hi, all.

On Thu, May 18, 2017 at 11:53 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 17.05.17 at 22:30, <julien.grall@xxxxxxx> wrote:
>> On 05/17/2017 07:51 PM, Oleksandr Tyshchenko wrote:
>>> On Wed, May 17, 2017 at 7:01 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> Well, if the ARM maintainers insist on baking their own thing every
>>>> time we'd use the M2P if it was there, I think I can't reasonably
>>>> block this patch. Otoh I'd prefer to not see the non-x86-specific
>>>> code move to x86/, so perhaps the whole patch wants
>>>> re-structuring using either a manifest definition in the ARM headers
>>>> or e.g. CONFIG_M2P (which x86 would select, but ARM wouldn't).
>>> Jan, I am afraid but I didn't get what you meant here:
>>> "manifest definition in the ARM headers"
>> I think he meant to have either a define in the header mentioning the
>> absence/presence of M2P.
> Yes, at least in a way.
>> But my preference would be using the Kconfig here.
> Depends on the symbol used: If such a symbol solely _indicates_
> the presence, Kconfig would be better indeed. If, however, the
> symbol is e.g. a macro resolving to a per-arch implementation,
> with common code providing a default definition when the arch
> doesn't provide any, then the non-Kconfig variant may be
> preferable.
> Jan

Thank you for your comments.
I have already posted a common comment regarding several patches in
the current series
as they are interrelated (please see patch #6), but I duplicate here
only related to this patch part.

patch #8: As we always allocate the page table for hardware domain,
this patch should be reworked.
The use_iommu flag should be set for both archs in case of hardware
domain. Having d->need_iommu set at the early stage we won't skip
IOMMU mapping updates anymore. And as the result the existing in
iommu_hwdom_init() code that goes through the list of page and tries
to retrieve mapping could be just dropped
instead of moving it to the arch-specific part.

Does the described above make sense?


Oleksandr Tyshchenko

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