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Re: [Xen-devel] [PATCH v2 33/34] xenbus: use virt_xxx barriers
- To: "Michael S. Tsirkin" <mst@xxxxxxxxxx>, <linux-kernel@xxxxxxxxxxxxxxx>
- From: David Vrabel <david.vrabel@xxxxxxxxxx>
- Date: Mon, 4 Jan 2016 11:32:00 +0000
- Cc: linux-mips@xxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, "H. Peter Anvin" <hpa@xxxxxxxxx>, sparclinux@xxxxxxxxxxxxxxx, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, linux-arch@xxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, Arnd Bergmann <arnd@xxxxxxxx>, x86@xxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, Ingo Molnar <mingo@xxxxxxx>, linux-xtensa@xxxxxxxxxxxxxxxx, user-mode-linux-devel@xxxxxxxxxxxxxxxxxxxxx, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>, adi-buildroot-devel@xxxxxxxxxxxxxxxxxxxxx, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, linux-metag@xxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, David Vrabel <david.vrabel@xxxxxxxxxx>, linuxppc-dev@xxxxxxxxxxxxxxxx, David Miller <davem@xxxxxxxxxxxxx>
- Delivery-date: Mon, 04 Jan 2016 11:32:16 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
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 an SMP host.
>
> Switch to virt_xxx barriers which serve this exact purpose.
Acked-by: David Vrabel <david.vrabel@xxxxxxxxxx>
If you're feeling particularly keen there's a rmb() consume_one_event()
in drivers/xen/events/events_fifo.c that can be converted to virt_rmb()
as well.
David
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