linux-kernel - Re: [PATCH v5 11/13] xen: introduce xen_alloc/free_coherent

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Message-ID: <20130905160905.GI11887@arm.com>
Date:	Thu, 5 Sep 2013 17:09:05 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"Ian.Campbell@...rix.com" <Ian.Campbell@...rix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>
Subject: Re: [PATCH v5 11/13] xen: introduce xen_alloc/free_coherent_pages

On Thu, Aug 29, 2013 at 07:32:32PM +0100, Stefano Stabellini wrote:
> xen_swiotlb_alloc_coherent needs to allocate a coherent buffer for cpu
> and devices. On native x86 and ARMv8 is sufficient to call
> __get_free_pages in order to get a coherent buffer, while on ARM we need
> to call arm_dma_ops.alloc.

Don't bet on this for ARMv8. It's not mandated for the architecture, so
at some point some SoC will require non-cacheable buffers for coherency.

-- 
Catalin
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