Re: [PATCH v7 resend 0/4] add generic vDPA device support

[longpeng2--- via <qemu-devel@nongnu.org>]

在 2022/11/6 13:22, Michael S. Tsirkin 写道:
> On Sun, Nov 06, 2022 at 08:17:07AM +0800, Longpeng (Mike, Cloud Infrastructure Service Product Dept.) wrote:
>>
>>
>> 在 2022/11/6 0:43, Michael S. Tsirkin 写道:
>>> On Sat, Nov 05, 2022 at 04:36:25PM +0800, Longpeng(Mike) wrote:
>>>> From: Longpeng <longpeng2@huawei.com>
>>>>
>>>> Hi guys,
>>>>
>>>> With the generic vDPA device, QEMU won't need to touch the device
>>>> types any more, such like vfio.
>>>
>>> With this kind of passthrough migration is completely MIA right?
>>> Better add a blocker...
>>
>> Oh, I missed the "vdpa-dev: mark the device as unmigratable" since v4 and
>> I'll add it in the next version.
>>
>> We'll support passthrough migration in the next step. We have already
>> written a demo that can migrate between some offloading cards.
> 
> Hmm ok. Backend disconnect can't work though, can it? State
> is by necessity lost when backend crashes.
>Yes, it can't.

>>> And given this is there an advantage over VFIO?
>>
>> I think the answer is the same as "why we need vDPA" if we compare it with
>> VFIO.
> 
> The answer is mostly because you can migrate and support backend
> disconnect, no?
>
Migrating between different hardware is the first consideration in our 
requirement, supporting backend disconnect is a low priority.

>>>
>>>> We can use the generic vDPA device as follow:
>>>>     -device vhost-vdpa-device-pci,vhostdev=/dev/vhost-vdpa-X
>>>>     Or
>>>>     -M microvm -m 512m -smp 2 -kernel ... -initrd ... -device \
>>>>     vhost-vdpa-device,vhostdev=/dev/vhost-vdpa-x
>>>
>>>> Changes v6 -> v7:
>>>>       (v6: https://mail.gnu.org/archive/html/qemu-devel/2022-05/msg02821.html)
>>>>       - rebase. [Jason]
>>>>       - add documentation . [Stefan]
>>>>
>>>> Changes v5 -> v6:
>>>>     Patch 2:
>>>>       - Turn to the original approach in the RFC to initialize the
>>>>         virtio_pci_id_info array. [Michael]
>>>> 	  https://lore.kernel.org/all/20220105005900.860-2-longpeng2@huawei.com/
>>>>     Patch 3:
>>>>       - Fix logical error of exception handler around the post_init.
>>>>         [Stefano]
>>>>       - Fix some coding style warnings. [Stefano]
>>>>     Patch 4:
>>>>       - Fix some coding style warnings. [Stefano]
>>>>
>>>> Changes v4 -> v5:
>>>>     Patch 3:
>>>>       - remove vhostfd [Jason]
>>>>       - support virtio-mmio [Jason]
>>>>
>>>> Changes v3 -> v4:
>>>>     v3: https://www.mail-archive.com/qemu-devel@nongnu.org/msg877015.html
>>>>     - reorganize the series [Stefano]
>>>>     - fix some typos [Stefano]
>>>>     - fix logical error in vhost_vdpa_device_realize [Stefano]
>>>>
>>>> Changes v2 -> v3
>>>>     Patch 4 & 5:
>>>>       - only call vdpa ioctls in vdpa-dev.c [Stefano, Longpeng]
>>>>       - s/VQS_NUM/VQS_COUNT  [Stefano]
>>>>       - check both vdpa_dev_fd and vdpa_dev [Stefano]
>>>>     Patch 6:
>>>>       - move all steps into vhost_vdpa_device_unrealize. [Stefano]
>>>>
>>>> Changes RFC -> v2
>>>>     Patch 1:
>>>>       - rename 'pdev_id' to 'trans_devid'  [Michael]
>>>>       - only use transitional device id for the devices
>>>>         listed in the spec  [Michael]
>>>>       - use macros to make the id_info table clearer  [Longpeng]
>>>>       - add some modern devices in the id_info table  [Longpeng]
>>>>     Patch 2:
>>>>       - remove the GET_VECTORS_NUM command  [Jason]
>>>>     Patch 4:
>>>>       - expose vdpa_dev_fd as a QOM preperty  [Stefan]
>>>>       - introduce vhost_vdpa_device_get_u32 as a common
>>>>         function to make the code clearer  [Stefan]
>>>>       - fix the misleading description of 'dc->desc'  [Stefano]
>>>>     Patch 5:
>>>>       - check returned number of virtqueues  [Stefan]
>>>>     Patch 6:
>>>>       - init s->num_queues  [Stefano]
>>>>       - free s->dev.vqs  [Stefano]
>>>>
>>>>
>>>> Longpeng (Mike) (4):
>>>>     virtio: get class_id and pci device id by the virtio id
>>>>     vdpa: add vdpa-dev support
>>>>     vdpa: add vdpa-dev-pci support
>>>>     docs: Add generic vhost-vdpa device documentation
>>>>
>>>>    docs/system/devices/vhost-vdpa-device.rst |  43 +++
>>>>    hw/virtio/Kconfig                         |   5 +
>>>>    hw/virtio/meson.build                     |   2 +
>>>>    hw/virtio/vdpa-dev-pci.c                  | 102 ++++++
>>>>    hw/virtio/vdpa-dev.c                      | 377 ++++++++++++++++++++++
>>>>    hw/virtio/virtio-pci.c                    |  88 +++++
>>>>    include/hw/virtio/vdpa-dev.h              |  43 +++
>>>>    include/hw/virtio/virtio-pci.h            |   5 +
>>>>    8 files changed, 665 insertions(+)
>>>>    create mode 100644 docs/system/devices/vhost-vdpa-device.rst
>>>>    create mode 100644 hw/virtio/vdpa-dev-pci.c
>>>>    create mode 100644 hw/virtio/vdpa-dev.c
>>>>    create mode 100644 include/hw/virtio/vdpa-dev.h
>>>>
>>>> -- 
>>>> 2.23.0
>>>
>>> .
> 
> 
> .