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([2a01:e0a:280:24f0:576b:abc6:6396:ed4a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b7908161e3sm2510783f8f.37.2025.07.29.06.19.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Jul 2025 06:19:45 -0700 (PDT) Message-ID: <9989340c-c304-4208-9c33-f54fc5d1e865@redhat.com> Date: Tue, 29 Jul 2025 15:19:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 02/20] hw/pci: Introduce pci_device_get_viommu_cap() To: Zhenzhong Duan , qemu-devel@nongnu.org Cc: alex.williamson@redhat.com, eric.auger@redhat.com, mst@redhat.com, jasowang@redhat.com, peterx@redhat.com, ddutile@redhat.com, jgg@nvidia.com, nicolinc@nvidia.com, shameerali.kolothum.thodi@huawei.com, joao.m.martins@oracle.com, clement.mathieu--drif@eviden.com, kevin.tian@intel.com, yi.l.liu@intel.com, chao.p.peng@intel.com References: <20250729092043.785836-1-zhenzhong.duan@intel.com> <20250729092043.785836-3-zhenzhong.duan@intel.com> Content-Language: en-US, fr From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= Autocrypt: addr=clg@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 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 Hello Zhenzhong On 7/29/25 11:20, Zhenzhong Duan wrote: > Introduce a new PCIIOMMUOps optional callback, get_viommu_cap() which > allows to retrieve capabilities exposed by a vIOMMU. The first planned vIOMMU device "device" is implied, but I find it easier to understand if it is stated openly. > capability is VIOMMU_CAP_HW_NESTED that advertises the support of HW > nested stage translation scheme. pci_device_get_viommu_cap is a wrapper > that can be called on a PCI device potentially protected by a vIOMMU. > > get_viommu_cap() is designed to return 64bit bitmap of purely emulated > capabilities which are only derermined by user's configuration, no host typo: determined > capabilities involved. Reasons are: > > 1. there can be more than one host IOMMUs with different capabilities "host IOMMU devices" Such as iommufd and VFIO IOMMU Type1 ? > 2. there can also be more than one vIOMMUs with different user > configuration, e.g., arm smmuv3. > 3. This is migration friendly, return value is consistent between source > and target. > 4. It's too late for VFIO to call get_viommu_cap() after set_iommu_device() > because we need get_viommu_cap() to determine if creating nested parent > hwpt or not at attaching stage, meanwhile hiod realize needs iommufd, hiod -> "host IOMMU device" > devid and hwpt_id which are ready after attach_device(). I find the above sentence difficult to understand. > See below sequence: > > attach_device() > get_viommu_cap() > create hwpt > ... > create hiod > set_iommu_device(hiod) > > Suggested-by: Yi Liu > Signed-off-by: Zhenzhong Duan > --- > MAINTAINERS | 1 + > include/hw/iommu.h | 17 +++++++++++++++++ > include/hw/pci/pci.h | 25 +++++++++++++++++++++++++ > hw/pci/pci.c | 11 +++++++++++ > 4 files changed, 54 insertions(+) > create mode 100644 include/hw/iommu.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index 37879ab64e..840cb1e604 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -2304,6 +2304,7 @@ F: include/system/iommufd.h > F: backends/host_iommu_device.c > F: include/system/host_iommu_device.h > F: include/qemu/chardev_open.h > +F: include/hw/iommu.h > F: util/chardev_open.c > F: docs/devel/vfio-iommufd.rst > > diff --git a/include/hw/iommu.h b/include/hw/iommu.h > new file mode 100644 > index 0000000000..021db50db5 > --- /dev/null > +++ b/include/hw/iommu.h > @@ -0,0 +1,17 @@ > +/* > + * General vIOMMU capabilities, flags, etc > + * > + * Copyright (C) 2025 Intel Corporation. > + * > + * SPDX-License-Identifier: GPL-2.0-or-later > + */ > + > +#ifndef HW_IOMMU_H > +#define HW_IOMMU_H > + > +enum { > + /* hardware nested stage-1 page table support */ > + VIOMMU_CAP_HW_NESTED = BIT_ULL(0), > +}; > + > +#endif /* HW_IOMMU_H */ > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h > index 6b7d3ac8a3..d89aefc030 100644 > --- a/include/hw/pci/pci.h > +++ b/include/hw/pci/pci.h > @@ -462,6 +462,21 @@ typedef struct PCIIOMMUOps { > * @devfn: device and function number of the PCI device. > */ > void (*unset_iommu_device)(PCIBus *bus, void *opaque, int devfn); > + /** > + * @get_viommu_cap: get vIOMMU capabilities > + * > + * Optional callback, if not implemented, then vIOMMU doesn't > + * support exposing capabilities to other subsystem, e.g., VFIO. > + * vIOMMU can choose which capabilities to expose. > + * > + * @opaque: the data passed to pci_setup_iommu(). > + * > + * Returns: 64bit bitmap with each bit represents a capability emulated by > + * VIOMMU_CAP_* in include/hw/iommu.h, these capabilities are theoretical > + * which are only determined by user's configuration and independent on the What is meant by "user's configuration" ? the vIOMMU device properties ? > + * actual host capabilities they may depend on. > + */ > + uint64_t (*get_viommu_cap)(void *opaque); > /** > * @get_iotlb_info: get properties required to initialize a device IOTLB. > * > @@ -642,6 +657,16 @@ bool pci_device_set_iommu_device(PCIDevice *dev, HostIOMMUDevice *hiod, > Error **errp); > void pci_device_unset_iommu_device(PCIDevice *dev); > > +/** > + * pci_device_get_viommu_cap: get vIOMMU capabilities. > + * > + * Returns a 64bit bitmap with each bit represents a vIOMMU exposed > + * capability, 0 if vIOMMU doesn't support esposing capabilities. exposing Thanks, C. > + * > + * @dev: PCI device pointer. > + */ > +uint64_t pci_device_get_viommu_cap(PCIDevice *dev); > + > /** > * pci_iommu_get_iotlb_info: get properties required to initialize a > * device IOTLB. > diff --git a/hw/pci/pci.c b/hw/pci/pci.c > index c70b5ceeba..df1fb615a8 100644 > --- a/hw/pci/pci.c > +++ b/hw/pci/pci.c > @@ -2992,6 +2992,17 @@ void pci_device_unset_iommu_device(PCIDevice *dev) > } > } > > +uint64_t pci_device_get_viommu_cap(PCIDevice *dev) > +{ > + PCIBus *iommu_bus; > + > + pci_device_get_iommu_bus_devfn(dev, &iommu_bus, NULL, NULL); > + if (iommu_bus && iommu_bus->iommu_ops->get_viommu_cap) { > + return iommu_bus->iommu_ops->get_viommu_cap(iommu_bus->iommu_opaque); > + } > + return 0; > +} > + > int pci_pri_request_page(PCIDevice *dev, uint32_t pasid, bool priv_req, > bool exec_req, hwaddr addr, bool lpig, > uint16_t prgi, bool is_read, bool is_write)