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Tsirkin" To: "Duan, Zhenzhong" Cc: "qemu-devel@nongnu.org" , "alex.williamson@redhat.com" , "clg@redhat.com" , "eric.auger@redhat.com" , "peterx@redhat.com" , "jasowang@redhat.com" , "jgg@nvidia.com" , "nicolinc@nvidia.com" , "joao.m.martins@oracle.com" , "Tian, Kevin" , "Liu, Yi L" , "Sun, Yi Y" , "Peng, Chao P" , Yi Sun , Paolo Bonzini , Richard Henderson , Eduardo Habkost , Marcel Apfelbaum Subject: Re: [PATCH v1 3/6] intel_iommu: Add a framework to check and sync host IOMMU cap/ecap Message-ID: <20240313030303-mutt-send-email-mst@kernel.org> References: <20240228094432.1092748-1-zhenzhong.duan@intel.com> <20240228094432.1092748-4-zhenzhong.duan@intel.com> <20240312130058-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.687, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Mar 13, 2024 at 02:52:39AM +0000, Duan, Zhenzhong wrote: > Hi Michael, > > >-----Original Message----- > >From: Michael S. Tsirkin > >Subject: Re: [PATCH v1 3/6] intel_iommu: Add a framework to check and > >sync host IOMMU cap/ecap > > > >On Wed, Feb 28, 2024 at 05:44:29PM +0800, Zhenzhong Duan wrote: > >> From: Yi Liu > >> > >> Add a framework to check and synchronize host IOMMU cap/ecap with > >> vIOMMU cap/ecap. > >> > >> The sequence will be: > >> > >> vtd_cap_init() initializes iommu->cap/ecap. > >> vtd_check_hdev() update iommu->cap/ecap based on host cap/ecap. > >> iommu->cap_frozen set when machine create done, iommu->cap/ecap > >become readonly. > >> > >> Implementation details for different backends will be in following patches. > >> > >> Signed-off-by: Yi Liu > >> Signed-off-by: Yi Sun > >> Signed-off-by: Zhenzhong Duan > >> --- > >> include/hw/i386/intel_iommu.h | 1 + > >> hw/i386/intel_iommu.c | 50 > >++++++++++++++++++++++++++++++++++- > >> 2 files changed, 50 insertions(+), 1 deletion(-) > >> > >> diff --git a/include/hw/i386/intel_iommu.h > >b/include/hw/i386/intel_iommu.h > >> index bbc7b96add..c71a133820 100644 > >> --- a/include/hw/i386/intel_iommu.h > >> +++ b/include/hw/i386/intel_iommu.h > >> @@ -283,6 +283,7 @@ struct IntelIOMMUState { > >> > >> uint64_t cap; /* The value of capability reg */ > >> uint64_t ecap; /* The value of extended capability reg */ > >> + bool cap_frozen; /* cap/ecap become read-only after frozen */ > >> > >> uint32_t context_cache_gen; /* Should be in [1,MAX] */ > >> GHashTable *iotlb; /* IOTLB */ > >> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c > >> index ffa1ad6429..a9f9dfd6a7 100644 > >> --- a/hw/i386/intel_iommu.c > >> +++ b/hw/i386/intel_iommu.c > >> @@ -35,6 +35,8 @@ > >> #include "sysemu/kvm.h" > >> #include "sysemu/dma.h" > >> #include "sysemu/sysemu.h" > >> +#include "hw/vfio/vfio-common.h" > >> +#include "sysemu/iommufd.h" > >> #include "hw/i386/apic_internal.h" > >> #include "kvm/kvm_i386.h" > >> #include "migration/vmstate.h" > >> @@ -3819,6 +3821,38 @@ VTDAddressSpace > >*vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, > >> return vtd_dev_as; > >> } > >> > >> +static int vtd_check_legacy_hdev(IntelIOMMUState *s, > >> + IOMMULegacyDevice *ldev, > >> + Error **errp) > >> +{ > >> + return 0; > >> +} > >> + > >> +static int vtd_check_iommufd_hdev(IntelIOMMUState *s, > >> + IOMMUFDDevice *idev, > >> + Error **errp) > >> +{ > >> + return 0; > >> +} > >> + > >> +static int vtd_check_hdev(IntelIOMMUState *s, VTDHostIOMMUDevice > >*vtd_hdev, > >> + Error **errp) > >> +{ > >> + HostIOMMUDevice *base_dev = vtd_hdev->dev; > >> + IOMMUFDDevice *idev; > >> + > >> + if (base_dev->type == HID_LEGACY) { > >> + IOMMULegacyDevice *ldev = container_of(base_dev, > >> + IOMMULegacyDevice, base); > >> + > >> + return vtd_check_legacy_hdev(s, ldev, errp); > >> + } > >> + > >> + idev = container_of(base_dev, IOMMUFDDevice, base); > >> + > >> + return vtd_check_iommufd_hdev(s, idev, errp); > >> +} > >> + > >> static int vtd_dev_set_iommu_device(PCIBus *bus, void *opaque, int > >devfn, > >> HostIOMMUDevice *base_dev, Error **errp) > >> { > >> @@ -3829,6 +3863,7 @@ static int vtd_dev_set_iommu_device(PCIBus > >*bus, void *opaque, int devfn, > >> .devfn = devfn, > >> }; > >> struct vtd_as_key *new_key; > >> + int ret; > >> > >> assert(base_dev); > >> > >> @@ -3848,6 +3883,13 @@ static int vtd_dev_set_iommu_device(PCIBus > >*bus, void *opaque, int devfn, > >> vtd_hdev->iommu_state = s; > >> vtd_hdev->dev = base_dev; > >> > >> + ret = vtd_check_hdev(s, vtd_hdev, errp); > >> + if (ret) { > >> + g_free(vtd_hdev); > >> + vtd_iommu_unlock(s); > >> + return ret; > >> + } > >> + > >> new_key = g_malloc(sizeof(*new_key)); > >> new_key->bus = bus; > >> new_key->devfn = devfn; > > > > > >Okay. So when VFIO device is created, it will call vtd_dev_set_iommu_device > >and that in turn will update caps. > > > > > > > > > >> @@ -4083,7 +4125,9 @@ static void vtd_init(IntelIOMMUState *s) > >> s->iq_dw = false; > >> s->next_frcd_reg = 0; > >> > >> - vtd_cap_init(s); > >> + if (!s->cap_frozen) { > >> + vtd_cap_init(s); > >> + } > >> > > > >If it's fronzen it's because VFIO was added after machine done. > >And then what? I think caps are just wrong? > > Not quite get your question on caps being wrong. But try to explains: > > When a hot plugged vfio device's host iommu cap isn't compatible with > vIOMMU's, hotplug should fail. Currently there is no check for this and > allow hotplug to succeed, but then some issue will reveal later, > e.g., vIOMMU's MGAW > host IOMMU's MGAW, guest can setup iova > mapping beyond host supported iova range, then DMA will fail. > > In fact, before this series, cap is not impacted by VFIO, so it's same effect of > frozen after machine done. > > > > > > >I think the way to approach this is just by specifying this > >as an option on command line. > > Do you mean add a cap_frozen property to intel_iommu? > Vtd_init() is called in realize() and system reset(), so I utilize realize() to init cap > and froze cap before system reset(). If cap_frozen is an option, when it's set to > false, cap could be updated every system reset and it's not a fix value any more. > This may break migration. No, I mean either 1. add some kind of vfio-iommu device that is not exposed to guest but is not hot pluggable or 2. add a property to specify ecap, rely on management to set it correctly > > > >So if one wants VFIO one has to sync caps with host. > >No? > > Yes, check for compatibility. But it's not preventing the usage of VFIO > with vIOMMU, it finds the incompatible issue earlier and fail hotplug instead of > surprising guest driver failure. > > Thanks > Zhenzhong I don't see where the check for compatibility and hotplug failure are. Did I miss it? > > > > > > > >> /* > >> * Rsvd field masks for spte > >> @@ -4254,6 +4298,10 @@ static int > >vtd_machine_done_notify_one(Object *child, void *unused) > >> > >> static void vtd_machine_done_hook(Notifier *notifier, void *unused) > >> { > >> + IntelIOMMUState *iommu = > >INTEL_IOMMU_DEVICE(x86_iommu_get_default()); > >> + > >> + iommu->cap_frozen = true; > >> + > >> object_child_foreach_recursive(object_get_root(), > >> vtd_machine_done_notify_one, NULL); > >> } > >> -- > >> 2.34.1