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

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Message-ID: <c01f684c-8b4d-1032-5e32-d9fa910d473e@intel.com>
Date:   Fri, 29 Sep 2023 10:56:33 -0700
From:   Jacob Keller <jacob.e.keller@...el.com>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        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>
CC:     <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 9/29/2023 5:15 AM, 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.
> ---

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>