From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH v5] xen/iommu: smmu: Advertise when the SMMU support coherent table walk Date: Mon, 2 Mar 2015 17:02:52 +0000 Message-ID: <1425315772.24959.18.camel@citrix.com> References: <1425310963-20948-1-git-send-email-julien.grall@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YSTlf-0001fV-KB for xen-devel@lists.xenproject.org; Mon, 02 Mar 2015 17:04:31 +0000 In-Reply-To: <1425310963-20948-1-git-send-email-julien.grall@linaro.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Julien Grall Cc: xen-devel@lists.xenproject.org, stefano.stabellini@citrix.com, tim@xen.org List-Id: xen-devel@lists.xenproject.org On Mon, 2015-03-02 at 15:42 +0000, Julien Grall wrote: > When SMMU doesn't support coherent table walk, Xen may need to clean > updated PT (see commit 4c5f4cb "xen/arm: p2m: Clean cache PT when the > IOMMU doesn't support coherent walk"). > > If one SMMU of the platform doesn't support coherent table walk, the > feature is disabled for the whole platform. This is because device is > assigned to a domain after the page table are populated. > > This could impact performance on domain which doesn't use device > passthrough. But, as the spec strongly recommends the support of this > feature for mainstream platform, I expect server will always have SMMUs > supporting coherent table walk. If not, we may need to enable this feature > per-domain. > > Signed-off-by: Julien Grall Acked + applied,thanks.