From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] [PATCH v2 33/34] xenbus: use virt_xxx barriers Date: Mon, 4 Jan 2016 11:32:00 +0000 Message-ID: <568A5830.9000501@citrix.com> References: <1451572003-2440-1-git-send-email-mst@redhat.com> <1451572003-2440-34-git-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1451572003-2440-34-git-send-email-mst@redhat.com> Sender: linux-ia64-owner@vger.kernel.org To: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org Cc: linux-mips@linux-mips.org, linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , virtualization@lists.linux-foundation.org, "H. Peter Anvin" , sparclinux@vger.kernel.org, Boris Ostrovsky , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Arnd Bergmann , x86@kernel.org, xen-devel@lists.xenproject.org, Ingo Molnar , linux-xtensa@linux-xtensa.org, user-mode-linux-devel@lists.sourceforge.net, Stefano Stabellini , adi-buildroot-devel@lists.sourceforge.net, Thomas Gleixner , linux-metag@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Andrew Cooper , David Vrabel , linuxppc-dev@lists.ozlabs.org, David Miller List-Id: linux-arch.vger.kernel.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 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp02.citrix.com ([66.165.176.63]:65176 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753137AbcADLcG (ORCPT ); Mon, 4 Jan 2016 06:32:06 -0500 Message-ID: <568A5830.9000501@citrix.com> Date: Mon, 4 Jan 2016 11:32:00 +0000 From: David Vrabel MIME-Version: 1.0 Subject: Re: [Xen-devel] [PATCH v2 33/34] xenbus: use virt_xxx barriers References: <1451572003-2440-1-git-send-email-mst@redhat.com> <1451572003-2440-34-git-send-email-mst@redhat.com> In-Reply-To: <1451572003-2440-34-git-send-email-mst@redhat.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org Cc: linux-mips@linux-mips.org, linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , virtualization@lists.linux-foundation.org, "H. Peter Anvin" , sparclinux@vger.kernel.org, Boris Ostrovsky , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Arnd Bergmann , x86@kernel.org, xen-devel@lists.xenproject.org, Ingo Molnar , linux-xtensa@linux-xtensa.org, user-mode-linux-devel@lists.sourceforge.net, Stefano Stabellini , adi-buildroot-devel@lists.sourceforge.net, Thomas Gleixner , linux-metag@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Andrew Cooper , David Vrabel , linuxppc-dev@lists.ozlabs.org, David Miller Message-ID: <20160104113200.2hZE9RPSn_YpOu0-Mc-JC3VIL8yAO0dfyrlNj2xsH-M@z> 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 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