From: Eric Auger <eric.auger@redhat.com>
To: "Tian, Kevin" <kevin.tian@intel.com>,
"Liu, Yi L" <yi.l.liu@intel.com>,
"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
"cohuck@redhat.com" <cohuck@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: "david@gibson.dropbear.id.au" <david@gibson.dropbear.id.au>,
"thuth@redhat.com" <thuth@redhat.com>,
"farman@linux.ibm.com" <farman@linux.ibm.com>,
"mjrosato@linux.ibm.com" <mjrosato@linux.ibm.com>,
"akrowiak@linux.ibm.com" <akrowiak@linux.ibm.com>,
"pasic@linux.ibm.com" <pasic@linux.ibm.com>,
"jjherne@linux.ibm.com" <jjherne@linux.ibm.com>,
"jasowang@redhat.com" <jasowang@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"jgg@nvidia.com" <jgg@nvidia.com>,
"nicolinc@nvidia.com" <nicolinc@nvidia.com>,
"eric.auger.pro@gmail.com" <eric.auger.pro@gmail.com>,
"Peng, Chao P" <chao.p.peng@intel.com>,
"Sun, Yi Y" <yi.y.sun@intel.com>,
"peterx@redhat.com" <peterx@redhat.com>
Subject: Re: [RFC 00/18] vfio: Adopt iommufd
Date: Mon, 25 Apr 2022 21:55:19 +0200 [thread overview]
Message-ID: <d1c63ea2-7396-7020-7a45-88e3d1918fb1@redhat.com> (raw)
In-Reply-To: <BN9PR11MB5276085CDF750807005A775B8CF39@BN9PR11MB5276.namprd11.prod.outlook.com>
Hi Kevin,
On 4/18/22 10:49 AM, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@intel.com>
>> Sent: Thursday, April 14, 2022 6:47 PM
>>
>> With the introduction of iommufd[1], the linux kernel provides a generic
>> interface for userspace drivers to propagate their DMA mappings to kernel
>> for assigned devices. This series does the porting of the VFIO devices
>> onto the /dev/iommu uapi and let it coexist with the legacy implementation.
>> Other devices like vpda, vfio mdev and etc. are not considered yet.
> vfio mdev has no special support in Qemu. Just that it's not supported
> by iommufd yet thus can only be operated in legacy container interface at
> this point. Later once it's supported by the kernel suppose no additional
> enabling work is required for mdev in Qemu.
>
>> For vfio devices, the new interface is tied with device fd and iommufd
>> as the iommufd solution is device-centric. This is different from legacy
>> vfio which is group-centric. To support both interfaces in QEMU, this
>> series introduces the iommu backend concept in the form of different
>> container classes. The existing vfio container is named legacy container
>> (equivalent with legacy iommu backend in this series), while the new
>> iommufd based container is named as iommufd container (may also be
>> mentioned
>> as iommufd backend in this series). The two backend types have their own
>> way to setup secure context and dma management interface. Below diagram
>> shows how it looks like with both BEs.
>>
>> VFIO AddressSpace/Memory
>> +-------+ +----------+ +-----+ +-----+
>> | pci | | platform | | ap | | ccw |
>> +---+---+ +----+-----+ +--+--+ +--+--+ +----------------------+
>> | | | | | AddressSpace |
>> | | | | +------------+---------+
>> +---V-----------V-----------V--------V----+ /
>> | VFIOAddressSpace | <------------+
>> | | | MemoryListener
>> | VFIOContainer list |
>> +-------+----------------------------+----+
>> | |
>> | |
>> +-------V------+ +--------V----------+
>> | iommufd | | vfio legacy |
>> | container | | container |
>> +-------+------+ +--------+----------+
>> | |
>> | /dev/iommu | /dev/vfio/vfio
>> | /dev/vfio/devices/vfioX | /dev/vfio/$group_id
>> Userspace | |
>>
>> ===========+============================+=======================
>> =========
>> Kernel | device fd |
>> +---------------+ | group/container fd
>> | (BIND_IOMMUFD | | (SET_CONTAINER/SET_IOMMU)
>> | ATTACH_IOAS) | | device fd
>> | | |
>> | +-------V------------V-----------------+
>> iommufd | | vfio |
>> (map/unmap | +---------+--------------------+-------+
>> ioas_copy) | | | map/unmap
>> | | |
>> +------V------+ +-----V------+ +------V--------+
>> | iommfd core | | device | | vfio iommu |
>> +-------------+ +------------+ +---------------+
> last row: s/iommfd/iommufd/
>
> overall this sounds a reasonable abstraction. Later when vdpa starts
> supporting iommufd probably the iommufd BE will become even
> smaller with more logic shareable between vfio and vdpa.
>
>> [Secure Context setup]
>> - iommufd BE: uses device fd and iommufd to setup secure context
>> (bind_iommufd, attach_ioas)
>> - vfio legacy BE: uses group fd and container fd to setup secure context
>> (set_container, set_iommu)
>> [Device access]
>> - iommufd BE: device fd is opened through /dev/vfio/devices/vfioX
>> - vfio legacy BE: device fd is retrieved from group fd ioctl
>> [DMA Mapping flow]
>> - VFIOAddressSpace receives MemoryRegion add/del via MemoryListener
>> - VFIO populates DMA map/unmap via the container BEs
>> *) iommufd BE: uses iommufd
>> *) vfio legacy BE: uses container fd
>>
>> This series qomifies the VFIOContainer object which acts as a base class
> what does 'qomify' mean? I didn't find this word from dictionary...
sorry this is pure QEMU terminology. This stands for "QEMU Object Model"
additional info at:
https://qemu.readthedocs.io/en/latest/devel/qom.html
Eric
>
>> for a container. This base class is derived into the legacy VFIO container
>> and the new iommufd based container. The base class implements generic
>> code
>> such as code related to memory_listener and address space management
>> whereas
>> the derived class implements callbacks that depend on the kernel user space
> 'the kernel user space'?
>
>> being used.
>>
>> The selection of the backend is made on a device basis using the new
>> iommufd option (on/off/auto). By default the iommufd backend is selected
>> if supported by the host and by QEMU (iommufd KConfig). This option is
>> currently available only for the vfio-pci device. For other types of
>> devices, it does not yet exist and the legacy BE is chosen by default.
>>
>> Test done:
>> - PCI and Platform device were tested
> In this case PCI uses iommufd while platform device uses legacy?
>
>> - ccw and ap were only compile-tested
>> - limited device hotplug test
>> - vIOMMU test run for both legacy and iommufd backends (limited tests)
>>
>> This series was co-developed by Eric Auger and me based on the exploration
>> iommufd kernel[2], complete code of this series is available in[3]. As
>> iommufd kernel is in the early step (only iommufd generic interface is in
>> mailing list), so this series hasn't made the iommufd backend fully on par
>> with legacy backend w.r.t. features like p2p mappings, coherency tracking,
> what does 'coherency tracking' mean here? if related to iommu enforce
> snoop it is fully handled by the kernel so far. I didn't find any use of
> VFIO_DMA_CC_IOMMU in current Qemu.
>
>> live migration, etc. This series hasn't supported PCI devices without FLR
>> neither as the kernel doesn't support VFIO_DEVICE_PCI_HOT_RESET when
>> userspace
>> is using iommufd. The kernel needs to be updated to accept device fd list for
>> reset when userspace is using iommufd. Related work is in progress by
>> Jason[4].
>>
>> TODOs:
>> - Add DMA alias check for iommufd BE (group level)
>> - Make pci.c to be BE agnostic. Needs kernel change as well to fix the
>> VFIO_DEVICE_PCI_HOT_RESET gap
>> - Cleanup the VFIODevice fields as it's used in both BEs
>> - Add locks
>> - Replace list with g_tree
>> - More tests
>>
>> Patch Overview:
>>
>> - Preparation:
>> 0001-scripts-update-linux-headers-Add-iommufd.h.patch
>> 0002-linux-headers-Import-latest-vfio.h-and-iommufd.h.patch
>> 0003-hw-vfio-pci-fix-vfio_pci_hot_reset_result-trace-poin.patch
>> 0004-vfio-pci-Use-vbasedev-local-variable-in-vfio_realize.patch
>> 0005-vfio-common-Rename-VFIOGuestIOMMU-iommu-into-
>> iommu_m.patch
> 3-5 are pure cleanups which could be sent out separately
>
>> 0006-vfio-common-Split-common.c-into-common.c-container.c.patch
>>
>> - Introduce container object and covert existing vfio to use it:
>> 0007-vfio-Add-base-object-for-VFIOContainer.patch
>> 0008-vfio-container-Introduce-vfio_attach-detach_device.patch
>> 0009-vfio-platform-Use-vfio_-attach-detach-_device.patch
>> 0010-vfio-ap-Use-vfio_-attach-detach-_device.patch
>> 0011-vfio-ccw-Use-vfio_-attach-detach-_device.patch
>> 0012-vfio-container-obj-Introduce-attach-detach-_device-c.patch
>> 0013-vfio-container-obj-Introduce-VFIOContainer-reset-cal.patch
>>
>> - Introduce iommufd based container:
>> 0014-hw-iommufd-Creation.patch
>> 0015-vfio-iommufd-Implement-iommufd-backend.patch
>> 0016-vfio-iommufd-Add-IOAS_COPY_DMA-support.patch
>>
>> - Add backend selection for vfio-pci:
>> 0017-vfio-as-Allow-the-selection-of-a-given-iommu-backend.patch
>> 0018-vfio-pci-Add-an-iommufd-option.patch
>>
>> [1] https://lore.kernel.org/kvm/0-v1-e79cd8d168e8+6-
>> iommufd_jgg@nvidia.com/
>> [2] https://github.com/luxis1999/iommufd/tree/iommufd-v5.17-rc6
>> [3] https://github.com/luxis1999/qemu/tree/qemu-for-5.17-rc6-vm-rfcv1
>> [4] https://lore.kernel.org/kvm/0-v1-a8faf768d202+125dd-
>> vfio_mdev_no_group_jgg@nvidia.com/
> Following is probably more relevant to [4]:
>
> https://lore.kernel.org/all/10-v1-33906a626da1+16b0-vfio_kvm_no_group_jgg@nvidia.com/
>
> Thanks
> Kevin
>
next prev parent reply other threads:[~2022-04-25 19:55 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-14 10:46 [RFC 00/18] vfio: Adopt iommufd Yi Liu
2022-04-14 10:46 ` [RFC 01/18] scripts/update-linux-headers: Add iommufd.h Yi Liu
2022-04-14 10:46 ` [RFC 02/18] linux-headers: Import latest vfio.h and iommufd.h Yi Liu
2022-04-14 10:46 ` [RFC 03/18] hw/vfio/pci: fix vfio_pci_hot_reset_result trace point Yi Liu
2022-04-14 10:46 ` [RFC 04/18] vfio/pci: Use vbasedev local variable in vfio_realize() Yi Liu
2022-04-14 10:46 ` [RFC 05/18] vfio/common: Rename VFIOGuestIOMMU::iommu into ::iommu_mr Yi Liu
2022-04-14 10:46 ` [RFC 07/18] vfio: Add base object for VFIOContainer Yi Liu
2022-04-29 6:29 ` David Gibson
2022-05-03 13:05 ` Yi Liu
2022-04-14 10:47 ` [RFC 08/18] vfio/container: Introduce vfio_[attach/detach]_device Yi Liu
2022-04-14 10:47 ` [RFC 09/18] vfio/platform: Use vfio_[attach/detach]_device Yi Liu
2022-04-14 10:47 ` [RFC 10/18] vfio/ap: " Yi Liu
2022-04-14 10:47 ` [RFC 11/18] vfio/ccw: " Yi Liu
2022-04-14 10:47 ` [RFC 12/18] vfio/container-obj: Introduce [attach/detach]_device container callbacks Yi Liu
2022-04-14 10:47 ` [RFC 13/18] vfio/container-obj: Introduce VFIOContainer reset callback Yi Liu
2022-04-14 10:47 ` [RFC 14/18] hw/iommufd: Creation Yi Liu
2022-04-14 10:47 ` [RFC 15/18] vfio/iommufd: Implement iommufd backend Yi Liu
2022-04-22 14:58 ` Jason Gunthorpe
2022-04-22 21:33 ` Alex Williamson
2022-04-26 9:55 ` Yi Liu
2022-04-26 10:41 ` Tian, Kevin
2022-04-26 13:41 ` Jason Gunthorpe
2022-04-26 14:08 ` Yi Liu
2022-04-26 14:11 ` Jason Gunthorpe
2022-04-26 18:45 ` Alex Williamson
2022-04-26 19:27 ` Jason Gunthorpe
2022-04-26 20:59 ` Alex Williamson
2022-04-26 23:08 ` Jason Gunthorpe
2022-04-26 13:53 ` Jason Gunthorpe
2022-04-14 10:47 ` [RFC 16/18] vfio/iommufd: Add IOAS_COPY_DMA support Yi Liu
2022-04-14 10:47 ` [RFC 17/18] vfio/as: Allow the selection of a given iommu backend Yi Liu
2022-04-14 10:47 ` [RFC 18/18] vfio/pci: Add an iommufd option Yi Liu
2022-04-15 8:37 ` [RFC 00/18] vfio: Adopt iommufd Nicolin Chen
2022-04-17 10:30 ` Eric Auger
2022-04-19 3:26 ` Nicolin Chen
2022-04-25 19:40 ` Eric Auger
2022-04-18 8:49 ` Tian, Kevin
2022-04-18 12:09 ` Yi Liu
2022-04-25 19:51 ` Eric Auger
2022-04-25 19:55 ` Eric Auger [this message]
2022-04-26 8:39 ` Tian, Kevin
2022-04-22 22:09 ` Alex Williamson
2022-04-25 10:10 ` Daniel P. Berrangé
2022-04-25 13:36 ` Jason Gunthorpe
2022-04-25 14:37 ` Alex Williamson
2022-04-26 8:37 ` Tian, Kevin
2022-04-26 12:33 ` Jason Gunthorpe
2022-04-26 16:21 ` Alex Williamson
2022-04-26 16:42 ` Jason Gunthorpe
2022-04-26 19:24 ` Alex Williamson
2022-04-26 19:36 ` Jason Gunthorpe
2022-04-28 3:21 ` Tian, Kevin
2022-04-28 14:24 ` Alex Williamson
2022-04-28 16:20 ` Daniel P. Berrangé
2022-04-29 0:45 ` Tian, Kevin
2022-04-25 20:23 ` Eric Auger
2022-04-25 22:53 ` Alex Williamson
2022-04-26 9:47 ` Shameerali Kolothum Thodi
2022-04-26 11:44 ` Eric Auger
2022-04-26 12:43 ` Shameerali Kolothum Thodi
2022-04-26 16:35 ` Alex Williamson
2022-05-09 14:24 ` Zhangfei Gao
2022-05-10 3:17 ` Yi Liu
2022-05-10 6:51 ` Eric Auger
2022-05-10 12:35 ` Zhangfei Gao
2022-05-10 12:45 ` Jason Gunthorpe
2022-05-10 14:08 ` Yi Liu
2022-05-11 14:17 ` zhangfei.gao
2022-05-12 9:01 ` zhangfei.gao
2022-05-17 8:55 ` Yi Liu
2022-05-18 7:22 ` zhangfei.gao
2022-05-18 14:00 ` Yi Liu
2022-06-28 8:14 ` Shameerali Kolothum Thodi
2022-06-28 8:58 ` Eric Auger
2022-05-17 8:52 ` Yi Liu
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