netdev - Re: [PATCH v5 virtio 02/11] virtio: allow caller to override device DMA mask in vp

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Date: Mon, 15 May 2023 10:54:12 +0800
From: Jason Wang <jasowang@...hat.com>
To: Shannon Nelson <shannon.nelson@....com>, mst@...hat.com,
 virtualization@...ts.linux-foundation.org, brett.creeley@....com,
 netdev@...r.kernel.org
Cc: simon.horman@...igine.com, drivers@...sando.io
Subject: Re: [PATCH v5 virtio 02/11] virtio: allow caller to override device
 DMA mask in vp_modern


在 2023/5/4 02:12, Shannon Nelson 写道:
> To add a bit of vendor flexibility with various virtio based devices,
> allow the caller to specify a different DMA mask.  This adds a dma_mask
> field to struct virtio_pci_modern_device.  If defined by the driver,
> this mask will be used in a call to dma_set_mask_and_coherent() instead
> of the traditional DMA_BIT_MASK(64).  This allows limiting the DMA space
> on vendor devices with address limitations.
>
> Signed-off-by: Shannon Nelson <shannon.nelson@....com>


Acked-by: Jason Wang <jasowang@...hat.com>

Thanks


> ---
>   drivers/virtio/virtio_pci_modern_dev.c | 3 ++-
>   include/linux/virtio_pci_modern.h      | 3 +++
>   2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
> index 9b2d6614de67..aad7d9296e77 100644
> --- a/drivers/virtio/virtio_pci_modern_dev.c
> +++ b/drivers/virtio/virtio_pci_modern_dev.c
> @@ -268,7 +268,8 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
>   		return -EINVAL;
>   	}
>   
> -	err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
> +	err = dma_set_mask_and_coherent(&pci_dev->dev,
> +					mdev->dma_mask ? : DMA_BIT_MASK(64));
>   	if (err)
>   		err = dma_set_mask_and_coherent(&pci_dev->dev,
>   						DMA_BIT_MASK(32));
> diff --git a/include/linux/virtio_pci_modern.h b/include/linux/virtio_pci_modern.h
> index e7b1db1dd0bb..067ac1d789bc 100644
> --- a/include/linux/virtio_pci_modern.h
> +++ b/include/linux/virtio_pci_modern.h
> @@ -41,6 +41,9 @@ struct virtio_pci_modern_device {
>   
>   	/* optional check for vendor virtio device, returns dev_id or -ERRNO */
>   	int (*device_id_check)(struct pci_dev *pdev);
> +
> +	/* optional mask for devices with limited DMA space */
> +	u64 dma_mask;
>   };
>   
>   /*