linux-kernel - Re: [Xen-devel] [PATCH 01/11] xen/arm: use dma-noncoherent.h calls for xen-swiotlb cache maintainance

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Message-ID: <20190826092001.GA13476@lst.de>
Date:   Mon, 26 Aug 2019 11:20:01 +0200
From:   Christoph Hellwig <hch@....de>
To:     Julien Grall <julien.grall@....com>
Cc:     Christoph Hellwig <hch@....de>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        xen-devel@...ts.xenproject.org, iommu@...ts.linux-foundation.org,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [Xen-devel] [PATCH 01/11] xen/arm: use dma-noncoherent.h calls
 for xen-swiotlb cache maintainance

On Mon, Aug 19, 2019 at 12:45:17PM +0100, Julien Grall wrote:
> On 8/16/19 2:00 PM, Christoph Hellwig wrote:
>> +static inline void xen_dma_map_page(struct device *hwdev, struct page *page,
>> +	     dma_addr_t dev_addr, unsigned long offset, size_t size,
>> +	     enum dma_data_direction dir, unsigned long attrs)
>> +{
>> +	unsigned long page_pfn = page_to_xen_pfn(page);
>> +	unsigned long dev_pfn = XEN_PFN_DOWN(dev_addr);
>> +	unsigned long compound_pages =
>> +		(1<<compound_order(page)) * XEN_PFN_PER_PAGE;
>> +	bool local = (page_pfn <= dev_pfn) &&
>> +		(dev_pfn - page_pfn < compound_pages);
>> +
>
> The Arm version as a comment here. Could we retain it?

I've added it in this patch, altough the rewrites later on mean it will
go away in favour of a new comment elsewhere anyway.