NACK/Cmnt: [SRU][Lunar][PATCH 0/1] UBUNTU: SAUCE: Add mdev_set_iommu_device() kABI.

[Stefan Bader]

On 25.04.23 21:45, Tarun Gupta wrote:
> BugLink : https://bugs.launchpad.net/bugs/1988806
> 
> SRU Justification:
> 
> [Impact]
> 
> Currently, with below commit present in 5.16 upstream kernel,
> mdev_set_iommu_device() kABI is removed.
> 
>   fda49d97f2c4 ("vfio: remove the unused mdev iommu hook")
> 
> This results in SRIOV based Nvidia vGPU being broken with kernels that
> have the above upstream commit present.
> So, with Ubuntu 22.04 HWE kernel update (i.e the 6.2.x Lunar kernel),
> SRIOV based Nvidia vGPU is broken.
> 
> Earlier, during 5.19.x HWE kernel in Kinetic release, a similar patch
> was accepted. Refer
> https://lists.ubuntu.com/archives/kernel-team/2022-September/133142.html
> But, this patch didn't get carry-forward from Kinetic to Lunar because
> of upstream merge conflict and had to be revert.
> 
> [Fix]
> 
> On 6.2.x HWE kernel, we revert the above patch which removed the
> support for mdev_set_iommu_device() kABI so that vGPU works fine.
> 
> [Testcase]
> 
> Run SRIOV based (Ampere+) Nvidia vGPU on 6.2.x (Lunar) kernel.
> 
> Tarun Gupta (1):
>    UBUNTU: SAUCE: Add mdev_set_iommu_device() kABI.
> 
>   drivers/vfio/mdev/mdev_driver.c  |   1 +
>   drivers/vfio/mdev/mdev_private.h |   1 -
>   drivers/vfio/vfio_iommu_type1.c  | 126 ++++++++++++++++++++++++++++---
>   include/linux/mdev.h             |  22 ++++++
>   4 files changed, 140 insertions(+), 10 deletions(-)
> 

Rejected for the following reasons:
- 23.04/Lunar has released now and stable release update criteria normally
   requires changes to be upstream
- For 22.10/Kinetic this seems to have been added to allow development
   before the release. The goal always should be to work on upstream
   solutions so hacks can be dropped when moving to the next release.
- Obviously this has not happened since 5.19, so before we accept this
   back into 6.2 I would like to see a plan moving forward as part of the
   SRU justification. So we avoid the same thing happening again on the
   next release which will become another HWE kernel in 22.04/Jammy.

-Stefan
-- 
- Stefan

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