From: Andrea Arcangeli <andrea@suse.de>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Eyal Lebedinsky <eyal@eyal.emu.id.au>, linux-kernel@vger.kernel.org
Subject: Re: 2.4.8aa1
Date: Sun, 12 Aug 2001 20:49:27 +0200 [thread overview]
Message-ID: <20010812204927.I737@athlon.random> (raw)
In-Reply-To: <20010812190202.H737@athlon.random> <Pine.LNX.4.33.0108121003520.15697-100000@penguin.transmeta.com>
In-Reply-To: <Pine.LNX.4.33.0108121003520.15697-100000@penguin.transmeta.com>; from torvalds@transmeta.com on Sun, Aug 12, 2001 at 10:21:58AM -0700
On Sun, Aug 12, 2001 at 10:21:58AM -0700, Linus Torvalds wrote:
>
> On Sun, 12 Aug 2001, Andrea Arcangeli wrote:
> >
> > virt_to_bus(page_address(pte_page(pte))) actually returns the right bus
> > address on x86 in a range of 4G,
>
> No it doesn't.
>
> page_address(page) is (page)->virtual, which is going to be zero for
> non-kmapped pages, and going to ve the virtual mapping of a kmapped page.
> NEITHER of which will translate correctly with "virt_to_bus()".
>
> In short, "virt_to_bus(page_address(pte_page(pte)))" only works for the
> first 1GB. Always have, always will.
Woops sorry, I was thinking at the 2.2 page_address, the 2.2 virt_to_bus
won't handle the warp around while the 2.4 does, in some bigmem patches
we used the 2.4 virt_to_bus just to allow
virt_to_bus(page_address(pte_page(pte))) to work up to 4G, this is why I
got mistaken. Of course in mainline 2.4 page_address(pte_page(pte)) is
just broken for any highmem page as you said.
Andrea
next prev parent reply other threads:[~2001-08-12 18:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-11 12:58 2.4.8aa1 Andrea Arcangeli
2001-08-11 13:32 ` 2.4.8aa1 Eyal Lebedinsky
2001-08-11 14:02 ` 2.4.8aa1 Andrea Arcangeli
2001-08-11 18:20 ` 2.4.8aa1 Linus Torvalds
2001-08-12 17:02 ` 2.4.8aa1 Andrea Arcangeli
2001-08-12 17:21 ` 2.4.8aa1 Linus Torvalds
2001-08-12 18:49 ` Andrea Arcangeli [this message]
2001-08-13 3:29 ` 2.4.8aa1 David S. Miller
2001-08-13 5:44 ` 2.4.8aa1 Linus Torvalds
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