Re: [Xen-devel] [PATCH v2 33/34] xenbus: use virt_xxx barriers

2016-01-04 Thread Stefano Stabellini
On Thu, 31 Dec 2015, Michael S. Tsirkin wrote: > drivers/xen/xenbus/xenbus_comms.c uses > full memory barriers to communicate with the other side. > > For guests compiled with CONFIG_SMP, smp_wmb and smp_mb > would be sufficient, so mb() and wmb() here are only needed if > a non-SMP guest runs on

Re: [Xen-devel] [PATCH v2 33/34] xenbus: use virt_xxx barriers

2016-01-04 Thread David Vrabel
On 31/12/15 19:10, Michael S. Tsirkin wrote: > drivers/xen/xenbus/xenbus_comms.c uses > full memory barriers to communicate with the other side. > > For guests compiled with CONFIG_SMP, smp_wmb and smp_mb > would be sufficient, so mb() and wmb() here are only needed if > a non-SMP guest runs on

Re: [Xen-devel] [PATCH v2 33/34] xenbus: use virt_xxx barriers

2016-01-04 Thread Peter Zijlstra
On Thu, Dec 31, 2015 at 09:10:01PM +0200, Michael S. Tsirkin wrote: > drivers/xen/xenbus/xenbus_comms.c uses > full memory barriers to communicate with the other side. > > For guests compiled with CONFIG_SMP, smp_wmb and smp_mb > would be sufficient, so mb() and wmb() here are only needed if > a

[Xen-devel] [PATCH v2 33/34] xenbus: use virt_xxx barriers

2015-12-31 Thread Michael S. Tsirkin
drivers/xen/xenbus/xenbus_comms.c uses full memory barriers to communicate with the other side. For guests compiled with CONFIG_SMP, smp_wmb and smp_mb would be sufficient, so mb() and wmb() here are only needed if a non-SMP guest runs on an SMP host. Switch to virt_xxx barriers which serve this