From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, Ian.Campbell@citrix.com
Subject: Re: [PATCH v5 12/13] swiotlb-xen: use xen_alloc/free_coherent_pages
Date: Fri, 6 Sep 2013 10:17:54 -0400 [thread overview]
Message-ID: <20130906141754.GT2590@phenom.dumpdata.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1309051743450.6397@kaball.uk.xensource.com>
On Thu, Sep 05, 2013 at 05:50:45PM +0100, Stefano Stabellini wrote:
> On Fri, 30 Aug 2013, Konrad Rzeszutek Wilk wrote:
> > On Thu, Aug 29, 2013 at 07:32:33PM +0100, Stefano Stabellini wrote:
> > > Use xen_alloc_coherent_pages and xen_free_coherent_pages to allocate or
> > > free coherent pages.
> > >
> > > We need to be careful handling the pointer returned by
> > > xen_alloc_coherent_pages, because on ARM the pointer is not equal to
> > > phys_to_virt(*dma_handle). In fact virt_to_phys on the returned pointer
> > > doesn't return a valid physical address.
> >
> > Why is it called 'virt_to_phys'? What does it return then?
>
> virt_to_phys only works for kernel direct mapped RAM memory.
> In this case the virtual address could be an ioremap address, therefore
> passing it to virt_to_phys would give you another physical address that
> doesn't correspond to it.
Ah, so very much ARM (and in some way SPARC) specific. I think you need add some comments
in the code (And git commit) to explain this. Thank you.
next prev parent reply other threads:[~2013-09-06 14:17 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-29 18:31 [PATCH v5 0/13] enable swiotlb-xen on arm and arm64 Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 01/13] arm: make SWIOTLB available Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 02/13] arm: introduce a global dma_ops pointer Stefano Stabellini
2013-09-02 14:45 ` [Xen-devel] " Julien Grall
2013-09-05 16:39 ` Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 03/13] arm64: define DMA_ERROR_CODE Stefano Stabellini
2013-09-05 16:05 ` Catalin Marinas
2013-09-05 16:54 ` Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 04/13] arm64: do not initialize arm64_swiotlb if dma_ops is already set Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 05/13] xen/arm, arm64: move Xen initialization earlier Stefano Stabellini
2013-09-05 16:20 ` [PATCH v5 05/13] xen/arm,arm64: " Catalin Marinas
2013-09-05 16:59 ` Stefano Stabellini
2013-09-06 8:58 ` Ian Campbell
2013-09-06 14:09 ` Catalin Marinas
2013-09-06 14:23 ` Konrad Rzeszutek Wilk
2013-09-06 14:53 ` Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 06/13] xen: introduce XENMEM_exchange_and_pin and XENMEM_unpin Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 07/13] xen: make xen_create_contiguous_region return the dma address Stefano Stabellini
2013-08-30 13:45 ` Konrad Rzeszutek Wilk
2013-08-29 18:32 ` [PATCH v5 08/13] swiotlb-xen: support autotranslate guests Stefano Stabellini
2013-08-30 13:46 ` Konrad Rzeszutek Wilk
2013-08-29 18:32 ` [PATCH v5 09/13] xen/arm,arm64: enable SWIOTLB_XEN Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 10/13] swiotlb-xen: introduce xen_swiotlb_set_dma_mask Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 11/13] xen: introduce xen_alloc/free_coherent_pages Stefano Stabellini
2013-09-05 16:09 ` Catalin Marinas
2013-09-05 16:43 ` Stefano Stabellini
2013-09-06 14:14 ` Catalin Marinas
2013-09-06 14:59 ` Stefano Stabellini
2013-09-06 15:59 ` Catalin Marinas
2013-09-06 16:09 ` Stefano Stabellini
2013-09-06 16:20 ` Catalin Marinas
2013-09-06 16:52 ` Stefano Stabellini
2013-09-09 15:51 ` Catalin Marinas
2013-09-09 16:46 ` Stefano Stabellini
2013-09-11 9:36 ` Catalin Marinas
2013-09-11 17:34 ` Stefano Stabellini
2013-09-12 13:53 ` Catalin Marinas
2013-09-12 14:44 ` Stefano Stabellini
2013-09-12 15:04 ` Catalin Marinas
2013-08-29 18:32 ` [PATCH v5 12/13] swiotlb-xen: use xen_alloc/free_coherent_pages Stefano Stabellini
2013-08-30 13:53 ` Konrad Rzeszutek Wilk
2013-09-05 16:50 ` Stefano Stabellini
2013-09-06 14:17 ` Konrad Rzeszutek Wilk [this message]
2013-09-06 15:04 ` Stefano Stabellini
2013-08-29 18:32 ` [PATCH v5 13/13] swiotlb: don't assume that io_tlb_start-io_tlb_end is coherent Stefano Stabellini
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