linux-kernel - Re: [PATCH V1 6/6] arm/xen: Assign xen-grant DMA ops for xen-grant DMA devices

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Date:   Sun, 24 Apr 2022 19:07:23 +0300
From:   Oleksandr <olekstysh@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Julien Grall <julien@....org>,
        "Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH V1 6/6] arm/xen: Assign xen-grant DMA ops for xen-grant
 DMA devices


On 23.04.22 19:42, Christoph Hellwig wrote:

Hello Christoph

> On Fri, Apr 22, 2022 at 07:51:03PM +0300, Oleksandr Tyshchenko wrote:
>>   static inline void xen_setup_dma_ops(struct device *dev)
>>   {
>>   #ifdef CONFIG_XEN
>> -	if (xen_swiotlb_detect())
>> +	if (arch_has_restricted_virtio_memory_access() &&
>> +			xen_is_grant_dma_device(dev))
>> +		xen_grant_setup_dma_ops(dev);
>> +	else if (xen_swiotlb_detect())
> I don't think that arch_has_restricted_virtio_memory_access
> check should be there as it still is a bit of a layering violation.

Well, I will remove it then (and update commit description).

For virtualized but non-virtio devices, it is not needed at all. For the 
virtio devices, this check is already present at 
virtio.c:virtio_features_ok()



>
-- 
Regards,

Oleksandr Tyshchenko