From: Bart Van Assche <Bart.VanAssche@sandisk.com>
To: Stefano Stabellini <sstabellini@kernel.org>
CC: "boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>,
        "jgross@suse.com" <jgross@suse.com>,
        "benh@kernel.crashing.org" <benh@kernel.crashing.org>,
        "dwmw2@infradead.org" <dwmw2@infradead.org>,
        "hpa@zytor.com" <hpa@zytor.com>, "mingo@redhat.com" <mingo@redhat.com>,
        "linux@armlinux.org.uk" <linux@armlinux.org.uk>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "julien.grall@arm.com" <julien.grall@arm.com>
Subject: Re: "Consolidate get_dma_ops" breaks Xen on ARM
Thread-Topic: "Consolidate get_dma_ops" breaks Xen on ARM
Thread-Index: AQHSslsHh7IRQQnwSE20JUn1iIdV7A==
Date: Tue, 11 Apr 2017 01:14:29 +0000
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On 04/10/17 17:31, Stefano Stabellini wrote:
> I think the reason is that, as you can see, if (dev && dev->dma_ops),
> dev->dma_ops is returned, while before this changes, xen_dma_ops was
> returned on Xen on ARM.
>
> Unfortunately DMA cannot work properly without using the appropriate
> xen_dma_ops. See drivers/xen/swiotlb-xen.c and arch/arm/xen/mm.c for
> more details. (The problem is easy to spot, but I wasn't CC'ed on the
> patch.)
>
> I don't know how to solve this problem without introducing some sort of
> if (xen()) in include/linux/dma-mapping.h.

Sorry but I don't have access to an ARM development system. Does your 
comment apply to dev == NULL only, dev != NULL only or perhaps to both? 
If your comment applies to dev != NULL only, can you check whether 
adding something like set_dma_ops(dev, get_arch_dma_ops(NULL)) to the 
appropriate ARM arch_setup_dma_ops() function is sufficient?

Thanks,

Bart.