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Wed, 5 Aug 2020 05:45:41 +0000 (UTC) Subject: Re: [RFC v2 1/1] memory: Delete assertion in memory_region_unregister_iommu_notifier To: Peter Xu , =?UTF-8?Q?Eugenio_P=c3=a9rez?= References: <20200628144746.GA239443@xz-x1> <54d2cdfd-97b8-9e1d-a607-d7a5e96be3a1@redhat.com> <20200629133403.GA266532@xz-x1> <2589d0e9-cc5b-a4df-8790-189b49f1a40e@redhat.com> <20200630153911.GD3138@xz-x1> <69f6d6e7-a0b1-abae-894e-4e81b7e0cc90@redhat.com> <20200702154540.GI40675@xz-x1> <34fe0e55-c0ae-8e56-462b-6281b6cca4f5@redhat.com> <7c17ff0c1be07c3e490fb02abb2b39a1d9f269b8.camel@redhat.com> <20200804203018.GD90726@xz-x1> From: Jason Wang Message-ID: <901112b8-c275-987b-d391-658cb3cf5988@redhat.com> Date: Wed, 5 Aug 2020 13:45:39 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200804203018.GD90726@xz-x1> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=207.211.31.120; envelope-from=jasowang@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/05 01:46:02 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_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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 , "Michael S. Tsirkin" , "libvir-list@redhat.com" , Juan Quintela , qemu-devel@nongnu.org, Eric Auger , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/8/5 上午4:30, Peter Xu wrote: > On Mon, Aug 03, 2020 at 06:00:34PM +0200, Eugenio Pérez wrote: >> On Fri, 2020-07-03 at 15:24 +0800, Jason Wang wrote: >>> On 2020/7/2 下午11:45, Peter Xu wrote: >>>> On Thu, Jul 02, 2020 at 11:01:54AM +0800, Jason Wang wrote: >>>>> So I think we agree that a new notifier is needed? >>>> Good to me, or a new flag should be easier (IOMMU_NOTIFIER_DEV_IOTLB)? >>> That should work but I wonder something as following is better. >>> >>> Instead of introducing new flags, how about carry the type of event in >>> the notifier then the device (vhost) can choose the message it want to >>> process like: >>> >>> static vhost_iommu_event(IOMMUNotifier *n, IOMMUTLBEvent *event) >>> >>> { >>> >>> switch (event->type) { >>> >>> case IOMMU_MAP: >>> case IOMMU_UNMAP: >>> case IOMMU_DEV_IOTLB_UNMAP: >>> ... >>> >>> } >>> >>> Thanks >>> >>> >> Hi! >> >> Sorry, I thought I had this clear but now it seems not so clear to me. Do you mean to add that switch to the current >> vhost_iommu_unmap_notify, and then the "type" field to the IOMMUTLBEntry? Is that the scope of the changes, or there is >> something I'm missing? >> >> If that is correct, what is the advantage for vhost or other notifiers? I understand that move the IOMMUTLBEntry (addr, >> len) -> (iova, mask) split/transformation to the different notifiers implementation could pollute them, but this is even a deeper change and vhost is not insterested in other events but IOMMU_UNMAP, isn't? >> >> On the other hand, who decide what type of event is? If I follow the backtrace of the assert in >> https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg01015.html, it seems to me that it should be >> vtd_process_device_iotlb_desc. How do I know if it should be IOMMU_UNMAP or IOMMU_DEV_IOTLB_UNMAP? If I set it in some >> function of memory.c, I should decide the type looking the actual notifier, isn't? > (Since Jason didn't reply yesterday, I'll try to; Jason, feel free to correct > me...) > > IMHO whether to put the type into the IOMMUTLBEntry is not important. The > important change should be that we introduce IOMMU_DEV_IOTLB_UNMAP (or I'd > rather call it IOMMU_DEV_IOTLB directly which is shorter and cleaner). With > that information we can make the failing assertion conditional for MAP/UNMAP > only. Or having another dedicated device IOTLB notifier. > We can also allow dev-iotlb messages to take arbitrary addr_mask (so it > becomes a length of address range; imho we can keep using addr_mask for > simplicity, but we can comment for addr_mask that for dev-iotlb it can be not a > real mask). Yes. Thanks > > Thanks, >