Re: [PATCH 00/21] Control VQ support in vDPA
From: Jason Wang
Date: Thu Dec 17 2020 - 04:04:58 EST
On 2020/12/17 下午3:58, Michael S. Tsirkin wrote:
On Thu, Dec 17, 2020 at 11:30:18AM +0800, Jason Wang wrote:
On 2020/12/16 下午5:47, Michael S. Tsirkin wrote:
On Wed, Dec 16, 2020 at 02:47:57PM +0800, Jason Wang wrote:
Hi All:
This series tries to add the support for control virtqueue in vDPA.
Control virtqueue is used by networking device for accepting various
commands from the driver. It's a must to support multiqueue and other
configurations.
When used by vhost-vDPA bus driver for VM, the control virtqueue
should be shadowed via userspace VMM (Qemu) instead of being assigned
directly to Guest. This is because Qemu needs to know the device state
in order to start and stop device correctly (e.g for Live Migration).
This requies to isolate the memory mapping for control virtqueue
presented by vhost-vDPA to prevent guest from accesing it directly.
To achieve this, vDPA introduce two new abstractions:
- address space: identified through address space id (ASID) and a set
of memory mapping in maintained
- virtqueue group: the minimal set of virtqueues that must share an
address space
How will this support the pretty common case where control vq
is programmed by the kernel through the PF, and others by the VFs?
In this case, the VF parent need to provide a software control vq and decode
the command then send them to VF.
But how does that tie to the address space infrastructure?
In this case, address space is not a must. But the idea is to make
control vq works for all types of hardware:
1) control virtqueue is implemented via VF/PF communication
2) control virtqueue is implemented by VF but not through DMA
3) control virtqueue is implemented by VF DMA, it could be either a
hardware control virtqueue or other type of DMA
The address space is a must for 3) to work and can work for both 1) and 2).
I actually thought the way to support it is by exposing
something like an "inject buffers" API which sends data to a given VQ.
Maybe an ioctl, and maybe down the road uio ring can support batching
these ....
So the virtuqueue allows the request to be processed asynchronously (e.g
driver may choose to use interrupt for control vq). This means we need to
support that in uAPI level.
I don't think we need to make it async, just a regular ioctl will do.
In fact no guest uses the asynchronous property.
It was not forbidden by the spec then we need to support that. E.g we
can not assume driver doesn't assign interrupt for cvq.
And if we manage to do that, it's just another
type of virtqueue.
For virtio-vDPA, this also means the extensions for queue processing which
is a functional duplication.
I don't see why, just send it to the actual control vq :)
But in the case you've pointed out, there's no hardware control vq in fact.
Using what proposed in this series, we don't
need any changes for kernel virtio drivers.
What's more important, this series could be used for future features that
requires DMA isolation between virtqueues:
- report dirty pages via virtqueue
- sub function level device slicing
I agree these are nice to have, but I am not sure basic control vq must
be tied to that.
If the control virtqueue is implemented via DMA through VF, it looks
like a must.
Thanks
...
Thanks
Device needs to advertise the following attributes to vDPA:
- the number of address spaces supported in the device
- the number of virtqueue groups supported in the device
- the mappings from a specific virtqueue to its virtqueue groups
The mappings from virtqueue to virtqueue groups is fixed and defined
by vDPA device driver. E.g:
- For the device that has hardware ASID support, it can simply
advertise a per virtqueue virtqueue group.
- For the device that does not have hardware ASID support, it can
simply advertise a single virtqueue group that contains all
virtqueues. Or if it wants a software emulated control virtqueue, it
can advertise two virtqueue groups, one is for cvq, another is for
the rest virtqueues.
vDPA also allow to change the association between virtqueue group and
address space. So in the case of control virtqueue, userspace
VMM(Qemu) may use a dedicated address space for the control virtqueue
group to isolate the memory mapping.
The vhost/vhost-vDPA is also extend for the userspace to:
- query the number of virtqueue groups and address spaces supported by
the device
- query the virtqueue group for a specific virtqueue
- assocaite a virtqueue group with an address space
- send ASID based IOTLB commands
This will help userspace VMM(Qemu) to detect whether the control vq
could be supported and isolate memory mappings of control virtqueue
from the others.
To demonstrate the usage, vDPA simulator is extended to support
setting MAC address via a emulated control virtqueue.
Please review.
Changes since RFC:
- tweak vhost uAPI documentation
- switch to use device specific IOTLB really in patch 4
- tweak the commit log
- fix that ASID in vhost is claimed to be 32 actually but 16bit
actually
- fix use after free when using ASID with IOTLB batching requests
- switch to use Stefano's patch for having separated iov
- remove unused "used_as" variable
- fix the iotlb/asid checking in vhost_vdpa_unmap()
Thanks
Jason Wang (20):
vhost: move the backend feature bits to vhost_types.h
virtio-vdpa: don't set callback if virtio doesn't need it
vhost-vdpa: passing iotlb to IOMMU mapping helpers
vhost-vdpa: switch to use vhost-vdpa specific IOTLB
vdpa: add the missing comment for nvqs in struct vdpa_device
vdpa: introduce virtqueue groups
vdpa: multiple address spaces support
vdpa: introduce config operations for associating ASID to a virtqueue
group
vhost_iotlb: split out IOTLB initialization
vhost: support ASID in IOTLB API
vhost-vdpa: introduce asid based IOTLB
vhost-vdpa: introduce uAPI to get the number of virtqueue groups
vhost-vdpa: introduce uAPI to get the number of address spaces
vhost-vdpa: uAPI to get virtqueue group id
vhost-vdpa: introduce uAPI to set group ASID
vhost-vdpa: support ASID based IOTLB API
vdpa_sim: advertise VIRTIO_NET_F_MTU
vdpa_sim: factor out buffer completion logic
vdpa_sim: filter destination mac address
vdpasim: control virtqueue support
Stefano Garzarella (1):
vdpa_sim: split vdpasim_virtqueue's iov field in out_iov and in_iov
drivers/vdpa/ifcvf/ifcvf_main.c | 9 +-
drivers/vdpa/mlx5/net/mlx5_vnet.c | 11 +-
drivers/vdpa/vdpa.c | 8 +-
drivers/vdpa/vdpa_sim/vdpa_sim.c | 292 ++++++++++++++++++++++++------
drivers/vhost/iotlb.c | 23 ++-
drivers/vhost/vdpa.c | 246 ++++++++++++++++++++-----
drivers/vhost/vhost.c | 23 ++-
drivers/vhost/vhost.h | 4 +-
drivers/virtio/virtio_vdpa.c | 2 +-
include/linux/vdpa.h | 42 ++++-
include/linux/vhost_iotlb.h | 2 +
include/uapi/linux/vhost.h | 25 ++-
include/uapi/linux/vhost_types.h | 10 +-
13 files changed, 561 insertions(+), 136 deletions(-)
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2.25.1