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From: Christoph Hellwig <hch@infradead.org>
To: Christopher Lameter <cl@linux.com>
Cc: Matthew Wilcox <willy@infradead.org>,
	Michal Hocko <mhocko@kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	"Luis R. Rodriguez" <mcgrof@kernel.org>,
	linux-mm@kvack.org, Jan Kara <jack@suse.cz>,
	matthew@wil.cx, x86@kernel.org, luto@amacapital.net,
	martin.petersen@oracle.com, jthumshirn@suse.de,
	broonie@kernel.org, linux-spi@vger.kernel.org,
	linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
	"lsf-pc@lists.linux-foundation.org"
	<lsf-pc@lists.linux-foundation.org>
Subject: Re: [LSF/MM TOPIC NOTES] x86 ZONE_DMA love
Date: Sat, 28 Apr 2018 01:33:47 -0700	[thread overview]
Message-ID: <20180428083347.GC31684@infradead.org> (raw)
In-Reply-To: <alpine.DEB.2.20.1804271136030.11686@nuc-kabylake>

On Fri, Apr 27, 2018 at 11:36:23AM -0500, Christopher Lameter wrote:
> On Fri, 27 Apr 2018, Matthew Wilcox wrote:
> 
> > Some devices have incredibly bogus hardware like 28 bit addressing
> > or 39 bit addressing.  We don't have a good way to allocate memory by
> > physical address other than than saying "GFP_DMA for anything less than
> > 32, GFP_DMA32 (or GFP_KERNEL on 32-bit) for anything less than 64 bit".
> >
> > Even CMA doesn't have a "cma_alloc_phys()".  Maybe that's the right place
> > to put such an allocation API.
> 
> The other way out of this would be to require a IOMMU?

Which on many systems doesn't exist.  And even if it exists might not
be usable.

  reply	other threads:[~2018-04-28  8:33 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-26 21:54 Luis R. Rodriguez
2018-04-27  1:09 ` [Lsf-pc] " Rik van Riel
2018-04-27  5:35 ` Christoph Hellwig
2018-04-27  7:18   ` Michal Hocko
2018-04-27 16:07     ` Christopher Lameter
2018-04-27 16:18       ` Matthew Wilcox
2018-04-27 16:36         ` Christopher Lameter
2018-04-28  8:33           ` Christoph Hellwig [this message]
2018-04-27 16:37       ` Michal Hocko
2018-04-28  8:33       ` Christoph Hellwig
2018-04-28  8:30     ` Christoph Hellwig
2018-04-27 16:14   ` Luis R. Rodriguez
2018-04-27 16:28     ` Matthew Wilcox
2018-04-28  8:42     ` Christoph Hellwig
2018-04-28 18:55       ` Luis R. Rodriguez
2018-04-28 19:46         ` Julia Lawall
2018-04-28 20:41           ` Matthew Wilcox
2018-04-29 14:34             ` Julia Lawall
     [not found]         ` <CAFhKne8u7KcBkpgiQ0fFZyh5_EorfY-_MJJaEYk3feCOd9LsRQ@mail.gmail.com>
2018-05-03 12:03           ` Michal Hocko
2018-05-03 12:13             ` Christoph Hellwig
2018-05-03  8:20 ` Geert Uytterhoeven
2018-05-05 16:08 ` Are media drivers abusing of GFP_DMA? - was: " Mauro Carvalho Chehab
2018-05-07 13:26   ` Laurent Pinchart
2018-05-07 15:19     ` Mauro Carvalho Chehab
2018-05-14  8:00       ` Fabien DESSENNE
2018-05-14 10:35         ` Mauro Carvalho Chehab
2018-05-14 10:39           ` Mauro Carvalho Chehab
2018-05-15  7:30             ` Fabien DESSENNE
2018-05-15  8:27               ` Laurent Pinchart
2018-05-15 10:30                 ` Mauro Carvalho Chehab
2018-05-15 16:24           ` Luis R. Rodriguez
2018-05-10  4:39   ` Yasunari.Takiguchi

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