Re: [PATCH] vdpa: Support setting vring_base for packed svq

[Sahil Siddiq <icegambit91@gmail.com>]

Hi,

On 11/14/24 12:28 PM, Michael S. Tsirkin wrote:
> On Mon, Nov 04, 2024 at 09:51:24PM +0530, Sahil Siddiq wrote:
>> Linux commit v5.14-rc1~30^2~8 enabled the vp_vdpa driver to set the
>> vq state to the device's initial state. This works differently for
>> split and packed vqs.
>>
>> With shadow virtqueues enabled, vhost-vdpa sets the vring base using
>> the VHOST_SET_VRING_BASE ioctl. The payload (vhost_vring_state)
>> differs for split and packed vqs. The implementation in QEMU currently
>> uses the payload required for split vqs (i.e., the num field of
>> vhost_vring_state is set to 0). The kernel throws EOPNOTSUPP when this
>> payload is used with packed vqs.
>>
>> This patch sets the num field in the payload appropriately so vhost-vdpa
>> (with the vp_vdpa driver) can use packed svqs.
>>
>> Link: https://lists.nongnu.org/archive/html/qemu-devel/2024-10/msg05106.html
>> Link: https://lore.kernel.org/r/20210602021536.39525-4-jasowang@redhat.com
>> Signed-off-by: Sahil Siddiq <sahilcdq@proton.me>
> 
> Looks like a feature, not a bugfix to me, so I guess - next release?
> 

Right. Also, based on the discussion in the reviews [1], it's been decided
to consider this patch for release when the patches to add support for
packed svqs [2] are also ready.

I'll resend this patch with the other patches.

Thanks,
Sahil

[1] https://lists.nongnu.org/archive/html/qemu-devel/2024-11/msg01432.html
[2] https://wiki.qemu.org/Internships/ProjectIdeas/PackedShadowVirtqueue