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Tue, 7 Jul 2020 08:03:12 +0000 (UTC) Subject: Re: [RFC v2 1/1] memory: Delete assertion in memory_region_unregister_iommu_notifier To: Peter Xu References: <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> <20200630153911.GD3138@xz-x1> <69f6d6e7-a0b1-abae-894e-4e81b7e0cc90@redhat.com> <20200702154540.GI40675@xz-x1> <34fe0e55-c0ae-8e56-462b-6281b6cca4f5@redhat.com> <20200703130338.GD6677@xz-x1> From: Jason Wang Message-ID: Date: Tue, 7 Jul 2020 16:03:10 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200703130338.GD6677@xz-x1> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; 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Tsirkin" , qemu-devel@nongnu.org, =?UTF-8?Q?Eugenio_P=c3=a9rez?= , Eric Auger , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/7/3 下午9:03, Peter Xu wrote: > On Fri, Jul 03, 2020 at 03:24:19PM +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: >> ... >> >> } > Looks ok to me, though imo we should still keep the registration information, > so VT-d knows which notifiers is interested in which events. E.g., we can > still do something like vtd_as_has_map_notifier(). Is this for a better performance? I wonder whether it's worth since we can't not have both vhost and vtd to be registered into the same as. So it should be functional equivalent to vtd_as_has_notifier(). Thanks > > So these are probably two different things: the new IOMMU_NOTIFIER_DEV_IOTLB > flag is one as discussed; the other one is whether we would like to introduce > IOMMUTLBEvent to include the type, so that we can avoid introduce two notifiers > for one device majorly to identify dev-iotlb from unmaps. > > Thanks, >