linux-kernel - Re: [Xen-devel] [PATCH] Revert "swiotlb: remove SWIOTLB_MAP

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Message-ID: <20190308152355.GA20230@lst.de>
Date:   Fri, 8 Mar 2019 16:23:55 +0100
From:   Christoph Hellwig <hch@....de>
To:     Julien Grall <julien.grall@....com>
Cc:     Arnd Bergmann <arnd@...db.de>, Robin Murphy <robin.murphy@....com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        xen-devel <xen-devel@...ts.xenproject.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [Xen-devel] [PATCH] Revert "swiotlb: remove SWIOTLB_MAP_ERROR"

On Tue, Mar 05, 2019 at 09:41:46AM +0000, Julien Grall wrote:
> On Xen, dma_addr_t will always be 64-bit while the phys_addr_t will depend 
> on the MMU type. So we may have phys_addr_t smaller than dma_addr_t from 
> the kernel point of view.

How can dma_addr_t on arm have value > 32-bit when physical
addresses are 32-bit only?