Re: [PATCH v2 4/6] x86/mem-paging: add minimal lock order enforcement to p2m_mem_paging_prep()

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, May 15, 2020 at 11:46:23AM +0200, Jan Beulich wrote:
> [CAUTION - EXTERNAL EMAIL] DO NOT reply, click links, or open attachments 
> unless you have verified the sender and know the content is safe.
> 
> On 14.05.2020 18:25, Roger Pau Monné wrote:
> > On Thu, Apr 23, 2020 at 10:38:44AM +0200, Jan Beulich wrote:
> >> While full checking is impossible (as the lock is being acquired/
> >> released down the call tree), perform at least a lock level check.
> > 
> > I'm slightly confused, doesn't alloc_domheap_page already have it's
> > own lock order checking?
> 
> I don't see how it would, as it doesn't (and can't legitimately)
> include arch/x86/mm/mm-locks.h. Also maybe this comment in the
> header clarifies it:
> 
> /* Page alloc lock (per-domain)
>  *
>  * This is an external lock, not represented by an mm_lock_t. However,
>  * pod code uses it in conjunction with the p2m lock, and expecting
>  * the ordering which we enforce here.
>  * The lock is not recursive. */


Thanks.

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>