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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: <20240313071647-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> <20240313030303-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 07:54:11AM +0000, Duan, Zhenzhong wrote: > > > >-----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, 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 > > Not quite get, what will such vfio-iommu device be used for if not exposed to guest. It will update the IOMMU. And do so without need for tricky callbacks. -- MST