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

[Jan Beulich <jbeulich@xxxxxxxx>]

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. */

Jan