From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36113) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cT2V0-0007Hg-Et for qemu-devel@nongnu.org; Mon, 16 Jan 2017 03:18:47 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cT2Ux-00036j-Bh for qemu-devel@nongnu.org; Mon, 16 Jan 2017 03:18:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51092) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cT2Ux-00036b-5V for qemu-devel@nongnu.org; Mon, 16 Jan 2017 03:18:39 -0500 Date: Mon, 16 Jan 2017 16:18:33 +0800 From: Peter Xu Message-ID: <20170116081833.GJ30108@pxdev.xzpeter.org> References: <1484276800-26814-1-git-send-email-peterx@redhat.com> <1484276800-26814-13-git-send-email-peterx@redhat.com> <397afe71-b4cd-ba48-6d76-a7b27e1128f9@redhat.com> <20170116074359.GD30108@pxdev.xzpeter.org> <8efe289b-e26a-60bc-51ae-582beff069fb@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <8efe289b-e26a-60bc-51ae-582beff069fb@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH RFC v3 12/14] intel_iommu: do replay when context invalidate List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Wang Cc: tianyu.lan@intel.com, kevin.tian@intel.com, mst@redhat.com, jan.kiszka@siemens.com, bd.aviv@gmail.com, qemu-devel@nongnu.org, alex.williamson@redhat.com On Mon, Jan 16, 2017 at 03:52:10PM +0800, Jason Wang wrote: >=20 >=20 > On 2017=E5=B9=B401=E6=9C=8816=E6=97=A5 15:43, Peter Xu wrote: > >On Mon, Jan 16, 2017 at 01:53:54PM +0800, Jason Wang wrote: > >> > >>On 2017=E5=B9=B401=E6=9C=8813=E6=97=A5 11:06, Peter Xu wrote: > >>>Before this one we only invalidate context cache when we receive con= text > >>>entry invalidations. However it's possible that the invalidation als= o > >>>contains a domain switch (only if cache-mode is enabled for vIOMMU). > >>So let's check for CM before replaying? > >When CM is not set, there should have no device needs > >IOMMU_NOTIFIER_MAP notifies. So IMHO it won't hurt if we replay here > >(so the notifier_list will only contain UNMAP notifiers at most, and > >sending UNMAP to those devices should not affect them at all). > > > >If we check CM before replay, it'll be faster when guest change iommu > >domain for a specific device. But after all this kind of operation is > >extremely rare, while if we check CM bit, we have a "assumption" in > >the code that MAP is depending on CM. In that case, to make the codes > >cleaner, I'd slightly prefer not check it here. How do you think? >=20 > Ok, I think maybe it's better to add a comment here. How about this? + /* + * So a device is moving out of (or moving into) a + * domain, a replay() suites here to notify all the + * IOMMU_NOTIFIER_MAP registers about this change. + * This won't bring bad even if we have no such + * notifier registered - the IOMMU notification + * framework will skip MAP notifications if that + * happened. + */ memory_region_iommu_replay_all(&vtd_as->iommu); Thanks, -- peterx