[PATCH 01/46] vfio: Introduce base object for VFIOContainer and targeted interface

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Zhou Wang

11 Jan 2025 11 Jan '25

10:52 a.m.

From: Zhenzhong Duan <zhenzhong.duan@intel.com> Introduce a dumb VFIOContainerBase object and its targeted interface. This is willingly not a QOM object because we don't want it to be visible from the user interface. The VFIOContainerBase will be smoothly populated in subsequent patches as well as interfaces. No functional change intended. Signed-off-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Yi Liu <yi.l.liu@intel.com> Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com> Reviewed-by: Cédric Le Goater <clg@redhat.com> Signed-off-by: Cédric Le Goater <clg@redhat.com> Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com> --- include/hw/vfio/vfio-common.h | 8 ++--- include/hw/vfio/vfio-container-base.h | 50 +++++++++++++++++++++++++++ 2 files changed, 52 insertions(+), 6 deletions(-) create mode 100644 include/hw/vfio/vfio-container-base.h diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h index fd9828d50b..c89b5886f2 100644 --- a/include/hw/vfio/vfio-common.h +++ b/include/hw/vfio/vfio-common.h @@ -30,6 +30,7 @@ #include <linux/vfio.h> #endif #include "sysemu/sysemu.h" +#include "hw/vfio/vfio-container-base.h" #define VFIO_MSG_PREFIX "vfio %s: " @@ -89,6 +90,7 @@ typedef struct VFIODMARange { } VFIODMARange; typedef struct VFIOContainer { + VFIOContainerBase bcontainer; VFIOAddressSpace *space; int fd; /* /dev/vfio/vfio, empowered by the attached groups */ MemoryListener listener; @@ -211,12 +213,6 @@ typedef struct VFIODisplay { } dmabuf; } VFIODisplay; -typedef struct { - unsigned long *bitmap; - hwaddr size; - hwaddr pages; -} VFIOBitmap; - VFIOAddressSpace *vfio_get_address_space(AddressSpace *as); void vfio_put_address_space(VFIOAddressSpace *space); bool vfio_devices_all_running_and_saving(VFIOContainer *container); diff --git a/include/hw/vfio/vfio-container-base.h b/include/hw/vfio/vfio-container-base.h new file mode 100644 index 0000000000..1d6daaea5d --- /dev/null +++ b/include/hw/vfio/vfio-container-base.h @@ -0,0 +1,50 @@ +/* + * VFIO BASE CONTAINER + * + * Copyright (C) 2023 Intel Corporation. + * Copyright Red Hat, Inc. 2023 + * + * Authors: Yi Liu <yi.l.liu@intel.com> + * Eric Auger <eric.auger@redhat.com> + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + +#ifndef HW_VFIO_VFIO_CONTAINER_BASE_H +#define HW_VFIO_VFIO_CONTAINER_BASE_H + +#include "exec/memory.h" + +typedef struct VFIODevice VFIODevice; +typedef struct VFIOIOMMUOps VFIOIOMMUOps; + +typedef struct { + unsigned long *bitmap; + hwaddr size; + hwaddr pages; +} VFIOBitmap; + +/* + * This is the base object for vfio container backends + */ +typedef struct VFIOContainerBase { + const VFIOIOMMUOps *ops; +} VFIOContainerBase; + +struct VFIOIOMMUOps { + /* basic feature */ + int (*dma_map)(VFIOContainerBase *bcontainer, + hwaddr iova, ram_addr_t size, + void *vaddr, bool readonly); + int (*dma_unmap)(VFIOContainerBase *bcontainer, + hwaddr iova, ram_addr_t size, + IOMMUTLBEntry *iotlb); + int (*attach_device)(const char *name, VFIODevice *vbasedev, + AddressSpace *as, Error **errp); + void (*detach_device)(VFIODevice *vbasedev); + /* migration feature */ + int (*set_dirty_page_tracking)(VFIOContainerBase *bcontainer, bool start); + int (*query_dirty_bitmap)(VFIOContainerBase *bcontainer, VFIOBitmap *vbmap, + hwaddr iova, hwaddr size); +}; +#endif /* HW_VFIO_VFIO_CONTAINER_BASE_H */ -- 2.33.0

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Zhou Wang

11 Jan 11 Jan

10:53 a.m.

New subject: [PATCH 46/46] docs/devel: Add VFIO iommufd backend documentation

From: Zhenzhong Duan <zhenzhong.duan@intel.com> Suggested-by: Cédric Le Goater <clg@redhat.com> Signed-off-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Yi Liu <yi.l.liu@intel.com> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com> Tested-by: Nicolin Chen <nicolinc@nvidia.com> Signed-off-by: Cédric Le Goater <clg@redhat.com> Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com> --- MAINTAINERS | 1 + docs/devel/index-internals.rst | 1 + docs/devel/vfio-iommufd.rst | 166 +++++++++++++++++++++++++++++++++ 3 files changed, 168 insertions(+) create mode 100644 docs/devel/vfio-iommufd.rst diff --git a/MAINTAINERS b/MAINTAINERS index ca70bb4e64..0ddb20a35f 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2176,6 +2176,7 @@ F: backends/iommufd.c F: include/sysemu/iommufd.h F: include/qemu/chardev_open.h F: util/chardev_open.c +F: docs/devel/vfio-iommufd.rst vhost M: Michael S. Tsirkin <mst@redhat.com> diff --git a/docs/devel/index-internals.rst b/docs/devel/index-internals.rst index 6f81df92bc..3def4a138b 100644 --- a/docs/devel/index-internals.rst +++ b/docs/devel/index-internals.rst @@ -18,5 +18,6 @@ Details about QEMU's various subsystems including how to add features to them. s390-dasd-ipl tracing vfio-migration + vfio-iommufd writing-monitor-commands virtio-backends diff --git a/docs/devel/vfio-iommufd.rst b/docs/devel/vfio-iommufd.rst new file mode 100644 index 0000000000..3d1c11f175 --- /dev/null +++ b/docs/devel/vfio-iommufd.rst @@ -0,0 +1,166 @@ +=============================== +IOMMUFD BACKEND usage with VFIO +=============================== + +(Same meaning for backend/container/BE) + +With the introduction of iommufd, the Linux kernel provides a generic +interface for user space drivers to propagate their DMA mappings to kernel +for assigned devices. While the legacy kernel interface is group-centric, +the new iommufd interface is device-centric, relying on device fd and iommufd. + +To support both interfaces in the QEMU VFIO device, introduce a base container +to abstract the common part of VFIO legacy and iommufd container. So that the +generic VFIO code can use either container. + +The base container implements generic functions such as memory_listener and +address space management whereas the derived container implements callbacks +specific to either legacy or iommufd. Each container has its own way to setup +secure context and dma management interface. The below diagram shows how it +looks like with both containers. + +:: + + VFIO AddressSpace/Memory + +-------+ +----------+ +-----+ +-----+ + | pci | | platform | | ap | | ccw | + +---+---+ +----+-----+ +--+--+ +--+--+ +----------------------+ + | | | | | AddressSpace | + | | | | +------------+---------+ + +---V-----------V-----------V--------V----+ / + | VFIOAddressSpace | <------------+ + | | | MemoryListener + | VFIOContainerBase 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 | + +-------------+ +------------+ +---------------+ + +* 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 + + 1. VFIOAddressSpace receives MemoryRegion add/del via MemoryListener + 2. VFIO populates DMA map/unmap via the container BEs + * iommufd BE: uses iommufd + * vfio legacy BE: uses container fd + +Example configuration +===================== + +Step 1: configure the host device +--------------------------------- + +It's exactly same as the VFIO device with legacy VFIO container. + +Step 2: configure QEMU +---------------------- + +Interactions with the ``/dev/iommu`` are abstracted by a new iommufd +object (compiled in with the ``CONFIG_IOMMUFD`` option). + +Any QEMU device (e.g. VFIO device) wishing to use ``/dev/iommu`` must +be linked with an iommufd object. It gets a new optional property +named iommufd which allows to pass an iommufd object. Take ``vfio-pci`` +device for example: + +.. code-block:: bash + + -object iommufd,id=iommufd0 + -device vfio-pci,host=0000:02:00.0,iommufd=iommufd0 + +Note the ``/dev/iommu`` and VFIO cdev can be externally opened by a +management layer. In such a case the fd is passed, the fd supports a +string naming the fd or a number, for example: + +.. code-block:: bash + + -object iommufd,id=iommufd0,fd=22 + -device vfio-pci,iommufd=iommufd0,fd=23 + +If the ``fd`` property is not passed, the fd is opened by QEMU. + +If no ``iommufd`` object is passed to the ``vfio-pci`` device, iommufd +is not used and the user gets the behavior based on the legacy VFIO +container: + +.. code-block:: bash + + -device vfio-pci,host=0000:02:00.0 + +Supported platform +================== + +Supports x86, ARM and s390x currently. + +Caveats +======= + +Dirty page sync +--------------- + +Dirty page sync with iommufd backend is unsupported yet, live migration is +disabled by default. But it can be force enabled like below, low efficient +though. + +.. code-block:: bash + + -object iommufd,id=iommufd0 + -device vfio-pci,host=0000:02:00.0,iommufd=iommufd0,enable-migration=on + +P2P DMA +------- + +PCI p2p DMA is unsupported as IOMMUFD doesn't support mapping hardware PCI +BAR region yet. Below warning shows for assigned PCI device, it's not a bug. + +.. code-block:: none + + qemu-system-x86_64: warning: IOMMU_IOAS_MAP failed: Bad address, PCI BAR? + qemu-system-x86_64: vfio_container_dma_map(0x560cb6cb1620, 0xe000000021000, 0x3000, 0x7f32ed55c000) = -14 (Bad address) + +FD passing with mdev +-------------------- + +``vfio-pci`` device checks sysfsdev property to decide if backend is a mdev. +If FD passing is used, there is no way to know that and the mdev is treated +like a real PCI device. There is an error as below if user wants to enable +RAM discarding for mdev. + +.. code-block:: none + + qemu-system-x86_64: -device vfio-pci,iommufd=iommufd0,x-balloon-allowed=on,fd=9: vfio VFIO_FD9: x-balloon-allowed only potentially compatible with mdev devices + +``vfio-ap`` and ``vfio-ccw`` devices don't have same issue as their backend +devices are always mdev and RAM discarding is force enabled. -- 2.33.0

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Zhou Wang

[PATCH 01/46] vfio: Introduce base object for VFIOContainer and targeted interface

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