Re: [PATCH v1 1/2] xen/arm: pci: introduce PCI_PASSTHROUGH Kconfig option

[Julien Grall <julien@xxxxxxx>]

Hi,

On 20/06/2023 16:29, Stewart Hildebrand wrote:
> From: Rahul Singh <rahul.singh@xxxxxxx>
>
> Setting CONFIG_PCI_PASSTHROUGH=y will enable PCI passthrough on ARM, even though
> the feature is not yet complete in the current upstream codebase. The purpose of
> this is to make it easier to enable the necessary configs (HAS_PCI, HAS_VPCI) 
> for
> testing and development of PCI passthrough on ARM.
>
> Since PCI passthrough on ARM is still work in progress at this time, make it
> depend on UNSUPPORTED.
>
> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
> ---
> (cherry picked from commit 9a08f1f7ce28ec619640ba9ce11018bf443e9a0e from the
>   downstream branch [1])
>
> Changes from downstream to v1:
> * depends on ARM_64 (Stefano)
> * Don't select HAS_VPCI_GUEST_SUPPORT since this config option is not currently
>    used in the upstream codebase. This will want to be re-added here once the
>    vpci series [2] is merged.
> * Don't select ARM_SMMU_V3 since this option can already be selected
>    independently. While PCI passthrough on ARM depends on an SMMU, it does not
>    depend on a particular version or variant of an SMMU.
> * Don't select HAS_ITS since this option can already be selected independently.
>    HAS_ITS may want to be added here once the MSI series [1] is merged.
> * Don't select LATE_HWDOM since this option is unrelated to PCI passthrough.
>
> [1] 
> https://gitlab.com/xen-project/people/bmarquis/xen-arm-poc/-/commits/poc/pci-passthrough
> [2] https://lists.xenproject.org/archives/html/xen-devel/2023-06/msg00863.html
> ---
>   xen/arch/arm/Kconfig | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> index 61e581b8c2b0..3d22cd26a68c 100644
> --- a/xen/arch/arm/Kconfig
> +++ b/xen/arch/arm/Kconfig
> @@ -184,6 +184,15 @@ config STATIC_SHM
>         help
>           This option enables statically shared memory on a dom0less system.
>   
> +config PCI_PASSTHROUGH
> +       bool "PCI passthrough on ARM (UNSUPPORTED)" if UNSUPPORTED
The series is already under an Arm category. So I would drop "ARM" here.

NIT: Also, I think it should be EXPERT rather than UNSUPPORTED. I view 
the former as in more "experimental" than the latter.
> +       depends on ARM_64
> +       select HAS_PCI
> +       select HAS_VPCI
> +       default n
> +       help
> +         PCI device passthrough on ARM (UNSUPPORTED)
Same.

> +
>   endmenu
>   
>   menu "ARM errata workaround via the alternative framework"
Cheers,

--
Julien Grall