linux-kernel - Re: [PATCH REGRESSION v2] iommu/apple-dart: Handle DMA_FQ domains in attach

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Date:   Fri, 22 Sep 2023 11:59:17 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Hector Martin <marcan@...can.st>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Joerg Roedel <jroedel@...e.de>, Neal Gompa <neal@...pa.dev>,
        "Justin M. Forbes" <jforbes@...oraproject.org>,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        asahi@...ts.linux.dev, stable@...r.kernel.org,
        regressions@...ts.linux.dev
Subject: Re: [PATCH REGRESSION v2] iommu/apple-dart: Handle DMA_FQ domains in
 attach_dev()

On Fri, Sep 22, 2023 at 11:55:23PM +0900, Hector Martin wrote:
> Commit a4fdd9762272 ("iommu: Use flush queue capability") hid the
> IOMMU_DOMAIN_DMA_FQ domain type from domain allocation. A check was
> introduced in iommu_dma_init_domain() to fall back if not supported, but
> this check runs too late: by that point, devices have been attached to
> the IOMMU, and apple-dart's attach_dev() callback does not expect
> IOMMU_DOMAIN_DMA_FQ domains.
> 
> Change the logic so the IOMMU_DOMAIN_DMA codepath is the default,
> instead of explicitly enumerating all types.
> 
> Fixes an apple-dart regression in v6.5.
> 
> Cc: regressions@...ts.linux.dev
> Cc: stable@...r.kernel.org
> Suggested-by: Robin Murphy <robin.murphy@....com>
> Fixes: a4fdd9762272 ("iommu: Use flush queue capability")
> Signed-off-by: Hector Martin <marcan@...can.st>
> ---
> Changes in v2:
> - Fixed the issue in apple-dart instead of the iommu core, per Robin's
>   suggestion.
> - Link to v1: https://lore.kernel.org/r/20230922-iommu-type-regression-v1-1-1ed3825b2c38@marcan.st
> ---
>  drivers/iommu/apple-dart.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

It is weird looking, but I have a followup series that will clean it -
this should go to -rc

Thanks,
Jason