linux-kernel - Re: [PATCH 1/1] s390/virtio_ccw: fix dma

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Message-ID: <875xq3yo97.fsf@linux.ibm.com>
Date: Tue, 08 Oct 2024 10:47:48 +0200
From: "Marc Hartmayer" <mhartmay@...ux.ibm.com>
To: Halil Pasic <pasic@...ux.ibm.com>, Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>, Eric Farman <farman@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger
 <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        "Martin
 K. Petersen" <martin.petersen@...cle.com>,
        Robin Murphy
 <robin.murphy@....com>,
        Ulf Hansson <ulf.hansson@...aro.org>, linux-s390@...r.kernel.org,
        virtualization@...ts.linux.dev, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] s390/virtio_ccw: fix dma_parm pointer not set up

On Mon, Oct 07, 2024 at 10:10 PM +0200, Halil Pasic <pasic@...ux.ibm.com> wrote:
> At least since commit 334304ac2bac ("dma-mapping: don't return errors
> from dma_set_max_seg_size") setting up device.dma_parms is basically
> mandated by the DMA API. As of now Channel (CCW) I/O in general does not
> utilize the DMA API, except for virtio. For virtio-ccw however the
> common virtio DMA infrastructure is such that most of the DMA stuff
> hinges on the virtio parent device, which is a CCW device.
>
> So lets set up the dma_parms pointer for the CCW parent device and hope
> for the best!
>
> Signed-off-by: Halil Pasic <pasic@...ux.ibm.com>
> Fixes: 334304ac2bac ("dma-mapping: don't return errors from dma_set_max_seg_size")
> Reported-by: "Marc Hartmayer" <mhartmay@...ux.ibm.com>
> Closes: https://bugzilla.linux.ibm.com/show_bug.cgi?id=209131

I guess, this line can be removed as it’s internal only.

> Reviewed-by: Eric Farman <farman@...ux.ibm.com>
> ---
>
> In the long run it may make sense to move dma_parms into struct
> ccw_device, since layering-wise it is much cleaner. I decided
> to put it in virtio_ccw_device because currently it is only used for
> virtio.
>
> ---

[…snip…]

Thanks for fixing this!

Tested-by: Marc Hartmayer <mhartmay@...ux.ibm.com>

-- 
Kind regards / Beste Grüße
   Marc Hartmayer

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