linux-kernel - Re: [PATCH] PCI/P2PDMA: Fix missing check for dma_virt

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Date:   Tue, 2 Jul 2019 18:37:26 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] PCI/P2PDMA: Fix missing check for dma_virt_ops

On Tue, Jul 02, 2019 at 11:35:44AM -0600, Logan Gunthorpe wrote:
> Drivers that use dma_virt_ops were meant to be rejected when testing
> compatibility for P2PDMA.
> 
> This check got inadvertantly dropped in one of the later versions of the
> original patchset, so add it back.
> 
> Fixes: 52916982af48 ("PCI/P2PDMA: Support peer-to-peer memory")
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>

Applied to pci/peer-to-peer for v5.3, thanks!

> ---
>  drivers/pci/p2pdma.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index a4994aa3acc0..ab48babdf214 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -487,6 +487,14 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
>  		return -1;
>  
>  	for (i = 0; i < num_clients; i++) {
> +		if (IS_ENABLED(CONFIG_DMA_VIRT_OPS) &&
> +		    clients[i]->dma_ops == &dma_virt_ops) {
> +			if (verbose)
> +				dev_warn(clients[i],
> +					 "cannot be used for peer-to-peer DMA because the driver makes use of dma_virt_ops\n");
> +			return -1;
> +		}
> +
>  		pci_client = find_parent_pci_dev(clients[i]);
>  		if (!pci_client) {
>  			if (verbose)
> @@ -765,7 +773,7 @@ int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
>  	 * p2pdma mappings are not compatible with devices that use
>  	 * dma_virt_ops. If the upper layers do the right thing
>  	 * this should never happen because it will be prevented
> -	 * by the check in pci_p2pdma_add_client()
> +	 * by the check in pci_p2pdma_distance_many()
>  	 */
>  	if (WARN_ON_ONCE(IS_ENABLED(CONFIG_DMA_VIRT_OPS) &&
>  			 dev->dma_ops == &dma_virt_ops))
> -- 
> 2.20.1
>