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Re: [Xen-devel] [PATCH v2 2/2] xen: implement VCPUOP_register_runstate_phys_memory_area

Hello Jan,

On 16.05.19 15:09, Jan Beulich wrote:
On 23.04.19 at 10:10, <andrii.anisov@xxxxxxxxx> wrote:
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -163,15 +163,23 @@ struct vcpu
      void            *sched_priv;    /* scheduler-specific data */
struct vcpu_runstate_info runstate;
+    spinlock_t      mapped_runstate_lock;

Besides other comments given elsewhere already - does this
really need to be a per-vCPU lock? Guests aren't expected to
invoke the API frequently, so quite likely a per-domain lock
would suffice. Quite possibly domain_{,un}lock() could
actually be (re-)used.

I'd not use a per-domain lock here. This lock will be locked on every runstate 
area update, what's happening on every context switch. And the event of 
simultaneous switching of vcpus from the same domain has quite high probability.

Andrii Anisov.

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