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Wed, 1 Jul 2020 12:30:08 +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> <1b4eaaaf-c2ab-0da8-afb4-1b7b4221e6cf@redhat.com> <20200630052148-mutt-send-email-mst@kernel.org> <49f547e1-dd87-7abe-1075-9dcece75b641@redhat.com> <20200630152050.GC3138@xz-x1> <20200701121626.GD40675@xz-x1> From: Jason Wang Message-ID: Date: Wed, 1 Jul 2020 20:30:07 +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: <20200701121626.GD40675@xz-x1> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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" , Juan Quintela , 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 2020/7/1 下午8:16, Peter Xu wrote: > On Wed, Jul 01, 2020 at 04:11:49PM +0800, Jason Wang wrote: >> On 2020/6/30 下午11:20, Peter Xu wrote: >>> On Tue, Jun 30, 2020 at 05:23:31PM +0800, Jason Wang wrote: >>>>>> 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"? >>> I was meaning "interrupt remapping", and of course it's the interrupt region >>> too when IR enabled... >> >> Right. >> >> >>>>>> 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? >>>> I meant a buggy(malicious) guest driver. >>> Yes seems possible. Do you want to post a patch? Let me know if you want me >>> to... Thanks, >> >> Yes please. > Oh wait... Actually the comment above explains... > > /* > * We have standalone memory region for interrupt addresses, we > * should never receive translation requests in this region. > */ > assert(!vtd_is_interrupt_addr(addr)); > > I overlooked myself that the IR region will be there even if ir=off. Yes, but the point stands still but the issue is still if ir=off. > So I > think the assert should stand. Do you mean vhost can't trigger the assert()? If yes, I don't get how it can't. Thanks >