Re: [PATCH v5 2/2] xen/arm: p2m: Populate pages for GICv2 mapping in p2m_init()

[Julien Grall <julien@xxxxxxx>]

Hi Henry,

On 18/10/2022 15:23, Henry Wang wrote:
> Hardware using GICv2 needs to create a P2M mapping of 8KB GICv2 area
> when the domain is created. Considering the worst case of page tables
> which requires 6 P2M pages as the two pages will be consecutive but not
> necessarily in the same L3 page table and keep a buffer, populate 16
> pages as the default value to the P2M pages pool in p2m_init() at the
> domain creation stage to satisfy the GICv2 requirement. For GICv3, the
> above-mentioned P2M mapping is not necessary, but since the allocated
> 16 pages here would not be lost, hence populate these pages
> unconditionally.
>
> With the default 16 P2M pages populated, there would be a case that
> failures would happen in the domain creation with P2M pages already in
> use. To properly free the P2M for this case, firstly support the
> optionally preemption of p2m_teardown(), then call p2m_teardown() and
> p2m_set_allocation(d, 0, NULL) non-preemptively in p2m_final_teardown().
> As non-preemptive p2m_teardown() should only return 0, use a
> BUG_ON to confirm that.
>
> Since p2m_final_teardown() is called either after
> domain_relinquish_resources() where relinquish_p2m_mapping() has been
> called, or from failure path of domain_create()/arch_domain_create()
> where mappings that require p2m_put_l3_page() should never be created,
> relinquish_p2m_mapping() is not added in p2m_final_teardown(), add
> in-code comments to refer this.
>
> Fixes: cbea5a1149ca ("xen/arm: Allocate and free P2M pages from the P2M pool")
> Suggested-by: Julien Grall <jgrall@xxxxxxxxxx>
> Signed-off-by: Henry Wang <Henry.Wang@xxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

I will commit it shortly. Regarding the backports, I will wait for a 
push in to staging/master before doing them.
Cheers,

--
Julien Grall