Re: [Xen-devel] [PATCH V5] xen/arm: Restrict "p2m_ipa_bits" according to the IOMMU requirements

[Julien Grall <julien.grall@xxxxxxx>]

On 27/09/2019 13:35, Julien Grall wrote:
> Hi,
>
> On 27/09/2019 12:57, Oleksandr Tyshchenko wrote:
> > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> >
> > There is a strict requirement for the IOMMU which wants to share
> > the P2M table with the CPU. The IOMMU's Stage-2 input size must be equal
> > to the P2M IPA size. It is not a problem when the IOMMU can support
> > all values the CPU supports. In that case, the IOMMU driver would just
> > use any "p2m_ipa_bits" value as is. But, there are cases when not.
> >
> > In order to make P2M sharing possible on the platforms which
> > IOMMUs have a limitation in maximum Stage-2 input size introduce
> > the following logic.
> >
> > First initialize the IOMMU subsystem and gather requirements regarding
> > the maximum IPA bits supported by each IOMMU device to figure out
> > the minimum value among them. In the P2M code, take into the account
> > the IOMMU requirements and choose suitable "pa_range" according
> > to the restricted "p2m_ipa_bits".
> >
> > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> > CC: Julien Grall <julien.grall@xxxxxxx>
> Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
Committed now. Thank you!

Cheers,

--
Julien Grall

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