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[79.182.31.92]) by smtp.gmail.com with ESMTPSA id h13sm2850675wml.42.2020.06.30.02.22.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2020 02:22:01 -0700 (PDT) Date: Tue, 30 Jun 2020 05:21:58 -0400 From: "Michael S. Tsirkin" To: Jason Wang Subject: Re: [RFC v2 1/1] memory: Delete assertion in memory_region_unregister_iommu_notifier Message-ID: <20200630052148-mutt-send-email-mst@kernel.org> References: <20200626064122.9252-1-eperezma@redhat.com> <20200626064122.9252-2-eperezma@redhat.com> <20200626212917.GD175520@xz-x1> <8cf25190-53e6-8cbb-372b-e3d4ec714dc5@redhat.com> <20200628144746.GA239443@xz-x1> <54d2cdfd-97b8-9e1d-a607-d7a5e96be3a1@redhat.com> <20200629133403.GA266532@xz-x1> <2589d0e9-cc5b-a4df-8790-189b49f1a40e@redhat.com> <1b4eaaaf-c2ab-0da8-afb4-1b7b4221e6cf@redhat.com> MIME-Version: 1.0 In-Reply-To: <1b4eaaaf-c2ab-0da8-afb4-1b7b4221e6cf@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=mst@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/30 00:34:33 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Yan Zhao , Juan Quintela , qemu-devel@nongnu.org, Peter Xu , Eugenio =?iso-8859-1?Q?P=E9rez?= , Eric Auger , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Jun 30, 2020 at 04:29:19PM +0800, Jason Wang wrote: > > On 2020/6/30 上午10:41, Jason Wang wrote: > > > > On 2020/6/29 下午9:34, Peter Xu wrote: > > > On Mon, Jun 29, 2020 at 01:51:47PM +0800, Jason Wang wrote: > > > > On 2020/6/28 下午10:47, Peter Xu wrote: > > > > > On Sun, Jun 28, 2020 at 03:03:41PM +0800, Jason Wang wrote: > > > > > > On 2020/6/27 上午5:29, Peter Xu wrote: > > > > > > > Hi, Eugenio, > > > > > > > > > > > > > > (CCing Eric, Yan and Michael too) > > > > > > > > > > > > > > On Fri, Jun 26, 2020 at 08:41:22AM +0200, Eugenio Pérez wrote: > > > > > > > > diff --git a/memory.c b/memory.c > > > > > > > > index 2f15a4b250..7f789710d2 100644 > > > > > > > > --- a/memory.c > > > > > > > > +++ b/memory.c > > > > > > > > @@ -1915,8 +1915,6 @@ void > > > > > > > > memory_region_notify_one(IOMMUNotifier > > > > > > > > *notifier, > > > > > > > >             return; > > > > > > > >         } > > > > > > > > -    assert(entry->iova >= notifier->start && > > > > > > > > entry_end <= notifier->end); > > > > > > > I can understand removing the assertion should solve > > > > > > > the issue, however imho > > > > > > > the major issue is not about this single assertion > > > > > > > but the whole addr_mask > > > > > > > issue behind with virtio... > > > > > > I don't get here, it looks to the the range was from > > > > > > guest IOMMU drivers. > > > > > Yes.  Note that I didn't mean that it's a problem in virtio, > > > > > it's just the fact > > > > > that virtio is the only one I know that would like to > > > > > support arbitrary address > > > > > range for the translated region.  I don't know about tcg, > > > > > but vfio should still > > > > > need some kind of page alignment in both the address and the > > > > > addr_mask.  We > > > > > have that assumption too across the memory core when we do > > > > > translations. > > > > > > > > Right but it looks to me the issue is not the alignment. > > > > > > > > > > > > > A further cause of the issue is the MSI region when vIOMMU > > > > > enabled - currently > > > > > we implemented the interrupt region using another memory > > > > > region so it split the > > > > > whole DMA region into two parts.  That's really a clean approach to IR > > > > > implementation, however that's also a burden to the > > > > > invalidation part because > > > > > then we'll need to handle things like this when the listened > > > > > range is not page > > > > > alighed at all (neither 0-0xfedffff, nor 0xfef0000-MAX).  If > > > > > without the IR > > > > > region (so the whole iommu address range will be a single FlatRange), > > > > > > > > Is this a bug? I remember that at least for vtd, it won't do any > > > > DMAR on the > > > > intrrupt address range > > > I don't think it's a bug, at least it's working as how I > > > understand...  that > > > interrupt range is using an IR region, that's why I said the IR > > > region splits > > > the DMAR region into two pieces, so we have two FlatRange for the same > > > IOMMUMemoryRegion. > > > > > > I don't check the qemu code but if "a single FlatRange" means > > 0xFEEx_xxxx is subject to DMA remapping, OS need to setup passthrough > > mapping for that range in order to get MSI to work. This is not what vtd > > spec said: > > > > """ > > > > 3.14 Handling Requests to Interrupt Address Range > > > > Requests without PASID to address range 0xFEEx_xxxx are treated as > > potential interrupt requests and are not subjected to DMA remapping > > (even if translation structures specify a mapping for this > > range). Instead, remapping hardware can be enabled to subject such > > interrupt requests to interrupt remapping. > > > > """ > > > > My understanding is vtd won't do any DMA translation on 0xFEEx_xxxx even > > if IR is not enabled. > > > Ok, we had a dedicated mr for interrupt: > > memory_region_add_subregion_overlap(MEMORY_REGION(&vtd_dev_as->iommu), > VTD_INTERRUPT_ADDR_FIRST, > &vtd_dev_as->iommu_ir, 1); > > So it should be fine. I guess the reason that I'm asking is that I thought > "IR" means "Interrupt remapping" but in fact it means "Interrupt Region"? > > But I'm still not clear about the invalidation part for interrupt region, > maybe you can elaborate a little more on this. > > Btw, I think guest can trigger the assert in vtd_do_iommu_translate() if we > teach vhost to DMA to that region: Why would we want to? > >     /* >      * We have standalone memory region for interrupt addresses, we >      * should never receive translation requests in this region. >      */ >     assert(!vtd_is_interrupt_addr(addr)); > > Is this better to return false here? (We can work on the fix for vhost but > it should be not trivial) > > Thanks >