From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 16 Aug 1999 23:41:50 -0700 (PDT) From: Linus Torvalds Subject: Re: [bigmem-patch] 4GB with Linux on IA32 In-Reply-To: <199908170637.XAA81444@google.engr.sgi.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Kanoj Sarcar Cc: Andrea Arcangeli , alan@lxorguk.ukuu.org.uk, sct@redhat.com, Gerhard.Wichert@pdb.siemens.de, Winfried.Gerhard@pdb.siemens.de, linux-kernel@vger.rutgers.edu, linux-mm@kvack.org List-ID: On Mon, 16 Aug 1999, Kanoj Sarcar wrote: > > As I pointed out before, I don't think rawio is the only case which > breaks. > > I will give you one example of the type of cases that I am talking about. > In drivers/char/bttv.c, VIDIOCSFBUF ioctl seems to be setting the "vidadr" > to a kernel virtual address from the physical address present in the > user's pte. This will not work for bigmem pages. This is exactly why I have always been adamant that people should NOT do direct IO and try to walk the page tables. But people have ignored me, and quite frankly, those drivers should just be broken. The painful part is finding out which of them do it, but once done they should just be broken wrt bigmem, no questions asked. Linus -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://humbolt.geo.uu.nl/Linux-MM/