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Wed, 15 Jan 2020 16:55:23 +0000 (UTC) Subject: Re: [PATCH v12 05/13] virtio-iommu: Endpoint and domains structs and helpers To: Peter Xu References: <20200109144319.15912-1-eric.auger@redhat.com> <20200109144319.15912-6-eric.auger@redhat.com> <20200113202301.GD201624@xz-x1> <51267d84-c805-a4a1-8084-b278721a5b3f@redhat.com> <20200114180734.GB225163@xz-x1> <20200115145949.GC233443@xz-x1> From: Auger Eric Message-ID: Date: Wed, 15 Jan 2020 17:55:21 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20200115145949.GC233443@xz-x1> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: w0KvfzskN1SbxspMeXOpvg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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@linaro.org, kevin.tian@intel.com, tnowicki@marvell.com, jean-philippe@linaro.org, quintela@redhat.com, qemu-devel@nongnu.org, dgilbert@redhat.com, bharatb.linux@gmail.com, qemu-arm@nongnu.org, mst@redhat.com, eric.auger.pro@gmail.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Peter, On 1/15/20 3:59 PM, Peter Xu wrote: > On Wed, Jan 15, 2020 at 02:00:22PM +0100, Auger Eric wrote: >> Hi Peter, >> >> >> On 1/14/20 7:07 PM, Peter Xu wrote: >>> On Tue, Jan 14, 2020 at 09:51:59AM +0100, Auger Eric wrote: >>>> Hi Peter, >>> >>> Hi, Eric, >>> >>> [...] >>> >>>>> >>>>>> +{ >>>>>> + VirtIOIOMMUEndpoint *ep; >>>>>> + >>>>>> + ep =3D g_tree_lookup(s->endpoints, GUINT_TO_POINTER(ep_id)); >>>>>> + if (ep) { >>>>>> + return ep; >>>>>> + } >>>>>> + if (!virtio_iommu_mr(s, ep_id)) { >>>>> >>>>> Could I ask when this will trigger? >>>> >>>> This can happen when a device is attached to a domain and its RID does >>>> not correspond to one of the devices protected by the iommu. >> >>> >>> So will it happen only because of a kernel driver bug? >> >> Yes, at the moment, because virtio_iommu_mr() only gets called on device >> attach to a domain. >> >> The spec says: >> "If the endpoint identified by endpoint doesn=E2=80=99t exist, the devic= e MUST >> reject the request and set status to VIRTIO_IOMMU_S_NOENT" >=20 > Sure. I just wanted to make sure I didn't miss anything, because I > really can't see when this extra logic can help, say, right now we > only have one vIOMMU at least for VT-d, so all devices will be managed > by that. But yeah if that's explicitly mentioned in the spec, I'd > agree we should follow that. >=20 >>> >>> Also, I think the name of "virtio_iommu_mr" is confusing on that it >>> returned explicitly a MemoryRegion however it's never been used: >> >> I use the same prototype as for smmu_iommu_mr(). Returning the iommu mr >> will allow to proceed with further RID based operations like invalidatio= ns. >> >> The same logic is used in vtd_context_device_invalidate. >=20 > I'm fine with this. Let's keep virtio_iommu_mr() as you prefer. >=20 > Another thing I'd like to mention is that, I don't think "the same > logic is used in VT-d" matters much. If we think something is wrong > (even if it's the same in VT-d), why not we fix both? :-) Sure ;-) Thank you for your time Eric >=20 > Thanks, >=20 >> >> >>> >>> (since they're not in the same patch I'm pasting) >>> >>> static IOMMUMemoryRegion *virtio_iommu_mr(VirtIOIOMMU *s, uint32_t sid) >>> { >>> uint8_t bus_n, devfn; >>> IOMMUPciBus *iommu_pci_bus; >>> IOMMUDevice *dev; >>> >>> bus_n =3D PCI_BUS_NUM(sid); >>> iommu_pci_bus =3D iommu_find_iommu_pcibus(s, bus_n); >>> if (iommu_pci_bus) { >>> devfn =3D sid & 0xFF; >>> dev =3D iommu_pci_bus->pbdev[devfn]; >>> if (dev) { >>> return &dev->iommu_mr; >>> } >>> } >>> return NULL; >>> } >>> >>> Maybe "return !!dev" would be enough, then make the return a boolean? >>> Then we can rename it to virtio_iommu_has_device(). >>> >>> PS. I think we can also drop IOMMU_PCI_DEVFN_MAX (after all you even >>> didn't use it here!) and use PCI_DEVFN_MAX, and replace 0xFF. >> well intel iommu and smmu use a similar constant (PCI_DEVFN_MAX, >> SMMU_PCI_DEVFN_MAX resp.). I use it in virtio_iommu_find_add_as >=20