From: "Gérard Roudier" <groudier@free.fr>
To: Andrea Arcangeli <andrea@suse.de>
Cc: Jens Axboe <axboe@suse.de>, "David S. Miller" <davem@redhat.com>,
<gibbs@scsiguy.com>, <LB33JM16@yahoo.com>,
<linux-kernel@vger.kernel.org>
Subject: Re: highmem, aic7xxx, and vfat: too few segs for dma mapping
Date: Wed, 12 Dec 2001 18:22:30 +0100 (CET) [thread overview]
Message-ID: <20011212181507.T1853-100000@gerard> (raw)
In-Reply-To: <20011212143213.E4801@athlon.random>
On Wed, 12 Dec 2001, Andrea Arcangeli wrote:
> On Wed, Dec 12, 2001 at 10:36:54AM +0100, Jens Axboe wrote:
> > > If one really wants for some marketing reason to support these ugly and
> > > stinky '32 bit machines that want to provide more than 4GB of memory by
> > > shoe-horning complexity all over the place', one should use his brain,
> > > when so-featured, prior to writing clueless code.
> >
> > First of all, virt_to_bus just cannot work on some archetectures that
> > are just slightly more advanced than x86. I'm quite sure Davem is ready
> > to lecture you on this.
>
> yes, the whole point of the iommu work (replacement for virt_to_bus) is
> for the 64bit machines, not for the 32bit machines. It's to allow the
> 64bit machines to do zerocopy dma (no bounce buffers) on memory above 4G
> with pci32 devices that doesn't support DAC.
So, the PCI group should just have specified a 16 bit BUS and have told
that systems should implement some IOMMU in order to address the whole
memory. :-)
PCI was intended to be implemented as a LOCAL BUS with all agents on the
LOCAL BUS being able to talk with any other agent using a flat addressing
scheme. Your PCI thing does not look like true PCI to me, but rather like
some bad mutant that has every chance not to survive a long time.
Gérard.
next prev parent reply other threads:[~2001-12-12 20:16 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-10 1:32 highmem, aic7xxx, and vfat: too few segs for dma mapping LBJM
2001-12-10 18:40 ` Justin T. Gibbs
2001-12-10 19:21 ` Jens Axboe
2001-12-10 19:50 ` Justin T. Gibbs
2001-12-10 20:03 ` Jens Axboe
2001-12-10 19:21 ` Gérard Roudier
2001-12-11 6:12 ` David S. Miller
2001-12-11 17:01 ` Gérard Roudier
2001-12-12 9:36 ` Jens Axboe
2001-12-12 13:32 ` Andrea Arcangeli
2001-12-12 17:22 ` Gérard Roudier [this message]
2001-12-12 22:19 ` Andrea Arcangeli
2001-12-12 20:24 ` Gérard Roudier
2001-12-13 0:26 ` David S. Miller
2001-12-13 16:17 ` Gérard Roudier
2001-12-13 20:30 ` David S. Miller
2001-12-13 18:13 ` Gérard Roudier
2001-12-13 0:06 ` David S. Miller
2001-12-13 16:39 ` Gérard Roudier
2001-12-12 16:39 ` Gérard Roudier
2001-12-13 20:10 ` Steve Lord
2001-12-13 20:15 ` Justin T. Gibbs
2001-12-13 20:29 ` Steve Lord
2001-12-13 20:48 ` Justin T. Gibbs
2001-12-13 20:58 ` Steve Lord
2001-12-13 21:27 ` David S. Miller
2001-12-14 15:16 ` Jens Axboe
2001-12-14 16:15 ` Jens Axboe
2001-12-14 16:22 ` Alok K. Dhir
2001-12-14 16:32 ` Jens Axboe
2001-12-14 16:25 ` Stephen Lord
2001-12-14 16:24 ` Jens Axboe
2001-12-13 21:17 ` Steve Lord
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