linux-kernel - Re: [PATCH v9 1/6] s390/ism: Set DMA coherent mask

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Message-ID: <20230516095819.78442f09@meshulam.tesarici.cz>
Date:   Tue, 16 May 2023 09:58:19 +0200
From:   Petr Tesařík <petr@...arici.cz>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        Wenjia Zhang <wenjia@...ux.ibm.com>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Gerd Bayer <gbayer@...ux.ibm.com>,
        Julian Ruess <julianr@...ux.ibm.com>,
        Pierre Morel <pmorel@...ux.ibm.com>,
        Alexandra Winter <wintera@...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>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Yong Wu <yong.wu@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Krishna Reddy <vdumpa@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Jonathan Corbet <corbet@....net>, linux-s390@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux.dev, asahi@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-tegra@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v9 1/6] s390/ism: Set DMA coherent mask

On Mon, 15 May 2023 11:15:51 +0200
Niklas Schnelle <schnelle@...ux.ibm.com> wrote:

> A future change will convert the DMA API implementation from the
> architecture specific arch/s390/pci/pci_dma.c to using the common code
> drivers/iommu/dma-iommu.c which the utilizes the same IOMMU hardware
> through the s390-iommu driver. Unlike the s390 specific DMA API this
> requires devices to correctly call set the coherent mask to be allowed
> to use IOVAs >2^32 in dma_alloc_coherent(). This was however not done
> for ISM devices. ISM requires such addresses since currently the DMA
> aperture for PCI devices starts at 2^32 and all calls to
> dma_alloc_coherent() would thus fail.
> 
> Reviewed-by: Alexandra Winter <wintera@...ux.ibm.com>
> Reviewed-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> ---
>  drivers/s390/net/ism_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c
> index 8acb9eba691b..1399b5dc646c 100644
> --- a/drivers/s390/net/ism_drv.c
> +++ b/drivers/s390/net/ism_drv.c
> @@ -660,7 +660,7 @@ static int ism_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	if (ret)
>  		goto err_disable;
>  
> -	ret = dma_set_mask(&pdev->dev, DMA_BIT_MASK(64));
> +	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));

Ah. I love this change. I have already wondered a few times if the
coherent DMA mask for this device may actually be different from
dma_mask. Now I know. ;-)

Thanks!

Petr T