From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Vrabel <david.vrabel@citrix.com>
Subject: Re: [PATCH v3 0/5] xen/arm: introduce
	GNTTABOP_cache_flush
Date: Wed, 8 Oct 2014 16:42:37 +0100
Message-ID: <54355B6D.2080005@citrix.com>
References: <alpine.DEB.2.02.1410081353510.17038@kaball.uk.xensource.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <alpine.DEB.2.02.1410081353510.17038@kaball.uk.xensource.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>, xen-devel@lists.xensource.com
Cc: Julien Grall <julien.grall@citrix.com>, Ian Campbell <Ian.Campbell@citrix.com>
List-Id: xen-devel@lists.xenproject.org

On 08/10/14 13:58, Stefano Stabellini wrote:
> Hi all,
> this patch series introduces a new hypercall to perform cache
> maintenance operations on behalf of the guest. It is useful for dom0 to
> be able to cache flush pages involved in a dma operation with
> non-coherent devices.

I was going to suggest requiring the use of the SWIOTLB for all foreign
pages to non-coherent devices but Ian tells me you've already tried this
and it performs worse than this proposal.  Is this the case?

Using the SWIOTLB would require no Xen changes (except for the revert)
which might be sensible at this point in the Xen 4.5 release cycle.

David