Re: [Xen-devel] [PATCH 02/57] ARM: vGICv3: clarify on GUEST_GICV3_RDIST_REGIONS symbol

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 05/03/18 16:03, Andre Przywara wrote:
> Normally there is only one GICv3 redistributor region, and we use
> that for DomU guests using a GICv3.
> Explain the background in a comment and why we need to keep the number
> of hardware regions for Dom0.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,

> ---
> Changelog RFC ... v1:
> - Keep GUEST_GICV3_RDIST_REGIONS symbol around, just extend comments
>
>   xen/arch/arm/vgic-v3.c | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
> index 2ad8a6be62..d5b34a7d0f 100644
> --- a/xen/arch/arm/vgic-v3.c
> +++ b/xen/arch/arm/vgic-v3.c
> @@ -1632,6 +1632,16 @@ static int vgic_v3_vcpu_init(struct vcpu *v)
>   
>   static inline unsigned int vgic_v3_rdist_count(struct domain *d)
>   {
> +    /*
> +     * Normally there is only one GICv3 redistributor region.
> +     * The GICv3 DT binding provisions for multiple regions, since there are
> +     * platforms out there which need those (multi-socket systems).
> +     * For Dom0 we have to live with the MMIO layout the hardware provides,
> +     * so we have to copy the multiple regions - as the first region may not
> +     * provide enough space to hold all redistributors we need.
> +     * However DomU get a constructed memory map, so we can go with
> +     * the architected single redistributor region.
> +     */
>       return is_hardware_domain(d) ? vgic_v3_hw.nr_rdist_regions :
>                  GUEST_GICV3_RDIST_REGIONS;
>   }
> @@ -1692,7 +1702,7 @@ static int vgic_v3_domain_init(struct domain *d)
>       {
>           d->arch.vgic.dbase = GUEST_GICV3_GICD_BASE;
>   
> -        /* XXX: Only one Re-distributor region mapped for the guest */
> +        /* A single Re-distributor region is mapped for the guest. */
>           BUILD_BUG_ON(GUEST_GICV3_RDIST_REGIONS != 1);
>   
>           d->arch.vgic.rdist_stride = GUEST_GICV3_RDIST_STRIDE;
--
Julien Grall

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