From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43497) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cVTrL-0002lX-VC for qemu-devel@nongnu.org; Sun, 22 Jan 2017 20:55:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cVTrH-0000DC-4Z for qemu-devel@nongnu.org; Sun, 22 Jan 2017 20:55:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57618) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cVTrG-0000Cy-VW for qemu-devel@nongnu.org; Sun, 22 Jan 2017 20:55:47 -0500 References: <1484917736-32056-1-git-send-email-peterx@redhat.com> <1484917736-32056-19-git-send-email-peterx@redhat.com> <490bbb84-213b-1b2a-5a1b-fa42a5c6a359@redhat.com> <20170122090425.GB26526@pxdev.xzpeter.org> From: Jason Wang Message-ID: <1dd223d1-dc02-bddc-02ea-78d267dd40a4@redhat.com> Date: Mon, 23 Jan 2017 09:55:39 +0800 MIME-Version: 1.0 In-Reply-To: <20170122090425.GB26526@pxdev.xzpeter.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH RFC v4 18/20] intel_iommu: enable vfio devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu 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 2017=E5=B9=B401=E6=9C=8822=E6=97=A5 17:04, Peter Xu wrote: > On Sun, Jan 22, 2017 at 04:08:04PM +0800, Jason Wang wrote: > > [...] > >>> +static void vtd_iotlb_page_invalidate_notify(IntelIOMMUState *s, >>> + uint16_t domain_id, hwadd= r addr, >>> + uint8_t am) >>> +{ >>> + IntelIOMMUNotifierNode *node; >>> + VTDContextEntry ce; >>> + int ret; >>> + >>> + QLIST_FOREACH(node, &(s->notifiers_list), next) { >>> + VTDAddressSpace *vtd_as =3D node->vtd_as; >>> + ret =3D vtd_dev_to_context_entry(s, pci_bus_num(vtd_as->bus)= , >>> + vtd_as->devfn, &ce); >>> + if (!ret && domain_id =3D=3D VTD_CONTEXT_ENTRY_DID(ce.hi)) { >>> + vtd_page_walk(&ce, addr, addr + (1 << am) * VTD_PAGE_SIZ= E, >>> + vtd_page_invalidate_notify_hook, >>> + (void *)&vtd_as->iommu, true); >> Why not simply trigger the notifier here? (or is this vfio required?) > Because we may only want to notify part of the region - we are with > mask here, but not exact size. > > Consider this: guest (with caching mode) maps 12K memory (4K*3 pages), > the mask will be extended to 16K in the guest. In that case, we need > to explicitly go over the page entry to know that the 4th page should > not be notified. I see. Then it was required by vfio only, I think we can add a fast path=20 for !CM in this case by triggering the notifier directly. Another possible issue is, consider (with CM) a 16K contiguous iova with=20 the last page has already been mapped. In this case, if we want to map=20 first three pages, when handling IOTLB invalidation, am would be 16K,=20 then the last page will be mapped twice. Can this lead some issue? Thanks