Re: [PATCH v2 2/3] xen/arm: make has_vpci depend on CONFIG_HAS_VPCI

[Julien Grall <julien@xxxxxxx>]

Hi,

On 07/07/2023 02:47, Stewart Hildebrand wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
>
> VPCI is disabled on ARM. Make it depend on CONFIG_HAS_VPCI to test the PCI
> passthrough support. Also make it depend on is_hardware_domain for now. The
> is_hardware_domain check should be removed when vPCI is upstreamed.
>
> While here, remove the comment on the preceding line.
>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
> ---
> There are two downstreams [1] [2] that have independently made a version this
> change, each with different Signed-off-by's. I simply picked one at random for
> the Author: field, and added both Signed-off-by lines. Please let me know if
> there are any objections.
>
> v1->v2:
> * add is_hardware_domain check. This will need to be removed after the vPCI
>    series [3] is merged.
>
> downstream->v1:
> * change to IS_ENABLED(CONFIG_HAS_VPCI) instead of hardcoded to true
> * remove the comment on the preceding line
>
> [1] 
> https://gitlab.com/xen-project/people/bmarquis/xen-arm-poc/-/commit/27be1729ce8128dbe37275ce7946b2fbd2e5a382
> [2] 
> https://github.com/xen-troops/xen/commit/bf12185e6fb2e31db0d8e6ea9ccd8a02abadec17
> [3] https://lists.xenproject.org/archives/html/xen-devel/2023-06/msg00863.html
> ---
>   xen/arch/arm/include/asm/domain.h | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/xen/arch/arm/include/asm/domain.h 
> b/xen/arch/arm/include/asm/domain.h
> index 99e798ffff68..1a13965a26b8 100644
> --- a/xen/arch/arm/include/asm/domain.h
> +++ b/xen/arch/arm/include/asm/domain.h
> @@ -298,8 +298,7 @@ static inline void arch_vcpu_block(struct vcpu *v) {}
>   
>   #define arch_vm_assist_valid_mask(d) (1UL << VMASST_TYPE_runstate_update_flag)
>   
> -/* vPCI is not available on Arm */
> -#define has_vpci(d)    ({ (void)(d); false; })
> +#define has_vpci(d) ({ IS_ENABLED(CONFIG_HAS_VPCI) && is_hardware_domain(d); })
So in v1, I asked whether we should use is_hardware_domain() or 
d->arch.pci. I see you went with the former, but wouldn't this mean that 
the vPCI is always enabled for dom0 when CONFIG_HAS_VPCI=y?
Shouldn't this instead be conditional to pci_passthrough_enabled?

So you could return d->arch.pci in has_vcpi(). The field would be set by 
domain_create() based on the flags passed by the caller. I would 
properly plumb to xen_domctl_createdomain and has a check in 
arch_sanitise_domain_config() to confirm the flag can be set.
Cheers,

--
Julien Grall