From: Andrea Arcangeli <andrea@suse.de>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Linus Torvalds <torvalds@transmeta.com>,
kanoj@google.engr.sgi.com, sct@redhat.com,
Gerhard.Wichert@pdb.siemens.de, Winfried.Gerhard@pdb.siemens.de,
linux-kernel@vger.rutgers.edu, linux-mm@kvack.org,
linux-usb@suse.com
Subject: Re: [bigmem-patch] 4GB with Linux on IA32
Date: Thu, 26 Aug 1999 18:27:51 +0200 (CEST) [thread overview]
Message-ID: <Pine.LNX.4.10.9908261811200.317-100000@laser.random> (raw)
In-Reply-To: <E11Ghah-0004RI-00@the-village.bc.nu>
On Tue, 17 Aug 1999, Alan Cox wrote:
>of bus addressses of vmalloc pages. I don't think the 4Gig patch breaks it
>at all. In the ideal world virt_to_bus() would work on vmalloc pages. It
Yes, the bigmem patch doesn't break bttv.
bttv alloc the DMA-pool via vmalloc and with the bigmem patch applyed
vmalloc prefere the bigmem pages so the DMA-pool will be always alloced
in bigmem memory.
But using vmalloc all bigmem pages will have a valid virt-to-phys
translation. (Only GFP may return a pointer without a valid virt-to-phys
translation if __GFP_BIGMEM is been specifyed in the gfp_mask.)
So the kernel can also copy-from/to-user the DMA pool using the vmalloc
addresses since it's a _valid_ address.
Via mmap the vmalloced pages will be remapped to userspace memory and
that's fine as well.
Andrea
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next prev parent reply other threads:[~1999-08-26 16:27 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-08-16 16:29 Andrea Arcangeli
1999-08-16 16:48 ` Matthew Wilcox
1999-08-16 17:19 ` Andrea Arcangeli
1999-08-16 18:43 ` Kanoj Sarcar
1999-08-16 19:43 ` Alan Cox
1999-08-16 20:54 ` Andrea Arcangeli
1999-08-16 22:47 ` Andrea Arcangeli
1999-08-16 23:26 ` Andrea Arcangeli
1999-08-16 23:39 ` Kanoj Sarcar
1999-08-17 0:10 ` Andrea Arcangeli
1999-08-17 6:37 ` Kanoj Sarcar
1999-08-17 6:41 ` Linus Torvalds
1999-08-17 6:50 ` Kanoj Sarcar
1999-08-17 7:03 ` Linus Torvalds
1999-08-17 7:23 ` Linus Torvalds
1999-08-17 11:39 ` Alan Cox
1999-08-26 16:27 ` Andrea Arcangeli [this message]
1999-08-17 11:46 ` Alan Cox
1999-08-17 14:26 ` Andrea Arcangeli
1999-08-17 6:39 ` Linus Torvalds
1999-08-17 12:40 ` Andrea Arcangeli
1999-08-17 6:29 ` Linus Torvalds
1999-08-17 12:37 ` Andrea Arcangeli
1999-08-17 14:04 ` Andrea Arcangeli
1999-08-17 8:52 ` Jakub Jelinek
1999-08-17 9:13 ` Pavel Machek
1999-08-18 14:08 ` Andrea Arcangeli
1999-08-19 12:20 ` Andrea Arcangeli
1999-08-16 23:28 ` Kanoj Sarcar
1999-08-16 23:49 ` Andrea Arcangeli
1999-08-17 6:29 ` David S. Miller
1999-08-17 12:38 ` Andrea Arcangeli
1999-08-17 0:17 ` Andrea Arcangeli
1999-08-19 13:33 ` Thierry Vignaud
1999-08-19 16:49 ` Stephen C. Tweedie
1999-08-20 7:35 ` Thierry Vignaud
1999-08-20 9:55 ` Alan Cox
1999-08-20 18:25 ` Linus Torvalds
1999-08-16 20:34 ` Andrea Arcangeli
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