From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH] virtio: Try to untangle DMA coherency Date: Fri, 10 Feb 2017 19:16:10 +0200 Message-ID: <20170210191409-mutt-send-email-mst@kernel.org> References: <8a6494f6409c20b4609cd6bdcdd751f68b5c0564.1485951731.git.robin.murphy@arm.com> <20170201195732-mutt-send-email-mst@kernel.org> <20170201182659.GM8177@arm.com> <20170201210648-mutt-send-email-mst@kernel.org> <20170202112614.GB30577@arm.com> <20170202182224-mutt-send-email-mst@kernel.org> <20170202164049.GI13839@arm.com> <20170209201341-mutt-send-email-mst@kernel.org> <20170209183118.GI19397@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20170209183118.GI19397@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Will Deacon Cc: mark.rutland@arm.com, devicetree@vger.kernel.org, pawel.moll@arm.com, virtualization@lists.linux-foundation.org, robh+dt@kernel.org, Robin Murphy , linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org On Thu, Feb 09, 2017 at 06:31:18PM +0000, Will Deacon wrote: > On ARM (and other archs such as > Power), having a mismatch between a cacheable and a non-cacheable mapping > can result in a loss of coherency between the two (for example, if the > non-cacheable gues accesses bypass the cache, but the cacheable host > accesses allocate in the cache). I guess it's an optimization to avoid cache snoops for non-cacheable accesses? -- MST