Re: [PATCH v3 3/4] xen/arm: Defer GICv2 CPU interface mapping until the first access

[Julien Grall <julien@xxxxxxx>]

Hi Henry,

On 28/03/2023 08:13, Henry Wang wrote:
> Currently, the mapping of the GICv2 CPU interface is created in
> arch_domain_create(). This causes some troubles in populating and
> freeing of the domain P2M pages pool. For example, a default 16
> P2M pages are required in p2m_init() to cope with the P2M mapping
> of 8KB GICv2 CPU interface area, and these 16 P2M pages would cause
> the complexity of P2M destroy in the failure path of
> arch_domain_create().
>
> As per discussion in [1], similarly as the MMIO access for ACPI, this
> patch defers the GICv2 CPU interface mapping until the first MMIO
> access. This is achieved by moving the GICv2 CPU interface mapping
> code from vgic_v2_domain_init()/vgic_v2_map_resources() to the
> stage-2 data abort trap handling code. The original CPU interface
> size and virtual CPU interface base address is now saved in
> `struct vgic_dist` instead of the local variable of
> vgic_v2_domain_init()/vgic_v2_map_resources().
>
> Take the opportunity to unify the way of data access using the
> existing pointer to struct vgic_dist in vgic_v2_map_resources() for
> new GICv2.
>
> Since gicv2_map_hwdom_extra_mappings() happens after domain_create(),
> so there is no need to map the extra mappings on-demand, and therefore
> keep the hwdom extra mappings as untouched.
>
> [1] 
> https://lore.kernel.org/xen-devel/e6643bfc-5bdf-f685-1b68-b28d341071c1@xxxxxxx/
>
> Signed-off-by: Henry Wang <Henry.Wang@xxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

--
Julien Grall