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

[Julien Grall <julien.grall@xxxxxxx>]

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>

Cheers,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel