Re: [PATCH net v3] net/mlx5: fix calling mlx5_cmd_init() before DMA mask is set

[Saeed Mahameed]

On 11 Oct 11:20, Saeed Mahameed wrote:
> On 11 Oct 09:57, Niklas Schnelle wrote:
> > Since commit 06cd555f73ca ("net/mlx5: split mlx5_cmd_init() to probe and
> > reload routines") mlx5_cmd_init() is called in mlx5_mdev_init() which is
> > called in probe_one() before mlx5_pci_init(). This is a problem because
> > mlx5_pci_init() is where the DMA and coherent mask is set but
> > mlx5_cmd_init() already does a dma_alloc_coherent(). Thus a DMA
> > allocation is done during probe before the correct mask is set. This
> > causes probe to fail initialization of the cmdif SW structs on s390x
> > after that is converted to the common dma-iommu code. This is because on
> > s390x DMA addresses below 4 GiB are reserved on current machines and
> > unlike the old s390x specific DMA API implementation common code
> > enforces DMA masks.
> >
> > Fix this by moving set_dma_caps() out of mlx5_pci_init() and into
> > probe_one() before mlx5_mdev_init(). To match the overall naming scheme
> > rename it to mlx5_dma_init().
>
> How about we just call mlx5_pci_init() before mlx5_mdev_init(), instead of
> breaking it apart ?

I just posted this RFC patch [1]:

I am working in very limited conditions these days, and I don't have strong
opinion on which approach to take, Leon, Niklas, please advise.

The three possible solutions:

1) mlx5_pci_init() before mlx5_mdev_init(), I don't think enabling pci
before initializing cmd dma would be a problem.

2) This patch.

3) Shay's patch from the link below:
[1] https://patchwork.kernel.org/project/netdevbpf/patch/20231011184511.19818-1-saeed@xxxxxxxxxx/

Thanks,
Saeed.