From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40175) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cK1Ad-0003fs-VG for qemu-devel@nongnu.org; Thu, 22 Dec 2016 06:04:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cK1Aa-00054W-J3 for qemu-devel@nongnu.org; Thu, 22 Dec 2016 06:04:23 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51008) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cK1Aa-00054C-Cl for qemu-devel@nongnu.org; Thu, 22 Dec 2016 06:04:20 -0500 Date: Thu, 22 Dec 2016 19:04:12 +0800 From: Peter Xu Message-ID: <20161222110412.GB26435@pxdev.xzpeter.org> References: <1482400096-23078-1-git-send-email-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v3] intel_iommu: allow dynamic switch of IOMMU region List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Wang Cc: qemu-devel@nongnu.org, tianyu.lan@intel.com, kevin.tian@intel.com, mst@redhat.com, jan.kiszka@siemens.com, alex.williamson@redhat.com, bd.aviv@gmail.com, david@gibson.dropbear.id.au On Thu, Dec 22, 2016 at 05:52:58PM +0800, Jason Wang wrote: >=20 >=20 > On 2016=E5=B9=B412=E6=9C=8822=E6=97=A5 17:48, Peter Xu wrote: > > /* Handle Translation Enable/Disable */ > > static void vtd_handle_gcmd_te(IntelIOMMUState *s, bool en) > > { > >+ if (s->dmar_enabled =3D=3D en) { > >+ return; > >+ } > >+ > > VTD_DPRINTF(CSR, "Translation Enable %s", (en ? "on" : "off")); > > if (en) { > >@@ -1196,6 +1237,8 @@ static void vtd_handle_gcmd_te(IntelIOMMUState *= s, bool en) > > /* Ok - report back to driver */ > > vtd_set_clear_mask_long(s, DMAR_GSTS_REG, VTD_GSTS_TES, 0); > > } > >+ > >+ vtd_switch_address_space_all(s, en); > > } >=20 > We may need something like notifier here to tell e.g vhost to stop devi= ce > IOTLB. (Since it's likely this series were applied after device IOTLB > patches) Yes, I missed vhost case. To notify vhost, IMO we should be able to use memory listeners just like how vfio devices do (please refer to vfio_memory_listener). However, I think the bigger issue is we still don't have a dynamic way to turn vhost DMAR on/off, right? If so, we may need to re-touch all the parts to enable the dynamic switching of DMA remapping - QEMU vhost, kernel vhost, and virtio on the guest side... I start to doubt whether that effort will worth it due to this single change, especially if this feature (dynamic on/off DMA remapping) won't be used by most VMs (i.e., Linux should only turn VT-d on when kernel detects it, and should never turn it off in anyway). (However I do think this is an improvement to current VT-d though) Thanks, -- peterx