From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@linaro.org>
Subject: Re: [PATCH v3 13/13] drivers/passthrough: arm: Add
 support for SMMU drivers
Date: Wed, 19 Mar 2014 10:44:19 +0000
Message-ID: <53297503.4010708@linaro.org>
References: <1394552999-14171-1-git-send-email-julien.grall@linaro.org>	
	<1394552999-14171-14-git-send-email-julien.grall@linaro.org>	
	<1395161689.11824.27.camel@kazak.uk.xensource.com>	
	<5328ABB6.3030307@linaro.org>
	<1395225305.10203.45.camel@kazak.uk.xensource.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta14.messagelabs.com ([193.109.254.103])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <julien.grall@linaro.org>) id 1WQDyw-0004Ap-VA
	for xen-devel@lists.xenproject.org; Wed, 19 Mar 2014 10:44:23 +0000
Received: by mail-we0-f180.google.com with SMTP id p61so6944934wes.11
	for <xen-devel@lists.xenproject.org>;
	Wed, 19 Mar 2014 03:44:21 -0700 (PDT)
In-Reply-To: <1395225305.10203.45.camel@kazak.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: Ian Campbell <Ian.Campbell@citrix.com>
Cc: xen-devel@lists.xenproject.org, Jan Beulich <jbeulich@suse.com>, tim@xen.org, Xiantao Zhang <xiantao.zhang@intel.com>, stefano.stabellini@citrix.com
List-Id: xen-devel@lists.xenproject.org

Hi Ian,

On 19/03/14 10:35, Ian Campbell wrote:
> On Tue, 2014-03-18 at 20:25 +0000, Julien Grall wrote:
>
>>>> +static __init void arm_smmu_device_reset(struct arm_smmu_device *smmu)
>>>> +{
>>>> +[...]
>>>> +    /* Don't upgrade barriers */
>>>> +    reg &= ~(SMMU_sCR0_BSU_MASK << SMMU_sCR0_BSU_SHIFT);
>>>
>>> No? Is that safe when a vcpu migrates around pCPUs?
>>
>>  From the SMMU doc 9.6.3, this field is only used when client devices are
>> not mapped to a translation context banks.
>>
>> By default, the policy in Xen is to deny every transaction that doesn't
>> have a valid mapping. So we are safe.
>>
>> I can update the comment if you want, or even better removing this code.
>
> I think adding the explanation you just gave would do the job. Even if
> you were to remove the code an explanation of why it doesn't mess with
> the BSU mask would still be valuable I think (but I think setting it to
> a known value even if it is unused would be best).

Ok. I will update the comment.

Regards,

-- 
Julien Grall