netdev - Re: [PATCH net v2] net/mlx5: fix calling mlx5_cmd

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Date: Sat, 30 Sep 2023 10:36:33 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: Saeed Mahameed <saeedm@...dia.com>, Jason Gunthorpe <jgg@...pe.ca>,
	Matthew Rosato <mjrosato@...ux.ibm.com>,
	Joerg Roedel <joro@...tes.org>, Robin Murphy <robin.murphy@....com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Shay Drory <shayd@...dia.com>, Moshe Shemesh <moshe@...dia.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	linux-s390@...r.kernel.org, netdev@...r.kernel.org,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2] net/mlx5: fix calling mlx5_cmd_init() before DMA
 mask is set

On Fri, Sep 29, 2023 at 02:15:49PM +0200, 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().
> 
> Link: https://lore.kernel.org/linux-iommu/cfc9e9128ed5571d2e36421e347301057662a09e.camel@linux.ibm.com/
> Fixes: 06cd555f73ca ("net/mlx5: split mlx5_cmd_init() to probe and reload routines")
> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> ---
> Note: I ran into this while testing the linked series for converting
> s390x to use dma-iommu. The existing s390x specific DMA API
> implementation doesn't respect DMA masks and is thus not affected
> despite of course also only supporting DMA addresses above 4 GiB.
> ---
> Changes in v2:
> - Instead of moving the whole mlx5_pci_init() only move the
>   set_dma_caps() call so as to keep pci_enable_device() after the FW
>   command interface initialization (Leon)
> - Link to v1: https://lore.kernel.org/r/20230928-mlx5_init_fix-v1-1-79749d45ce60@linux.ibm.com
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/main.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 

Thanks,
Reviewed-by: Leon Romanovsky <leonro@...dia.com>