From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: RE: [git pull] x86 PAT changes
Date: Sat, 26 Apr 2008 10:15:33 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.1.10.0804261011030.2813@woody.linux-foundation.org> (raw)
In-Reply-To: <924EFEDD5F540B4284297C4DC59F3DEEF313A6@orsmsx423.amr.corp.intel.com>
On Sat, 26 Apr 2008, Pallipadi, Venkatesh wrote:
>
> Agreed that NONPROMISC_DEVMEM is not really needed for read/write. But,
> we will still need it for /dev/mem.
If so, just disable it unconditionally for mmap.
As mentioned, that's really just a return to original Linux /dev/mmap
semantics: long ago (well, not _that_ long ago) we never used to be able
to mmap() normal kernel memory, because the page counts would get screwed
up on pages that weren't marked PG_Reserved.
So the traditional Linux behavior for mmap() on /dev/mem was always to
only allow it on memory that either had no "struct page *" backing at all,
or that was marked PG_Reserved (ie the ISA hole ay 640k-1M and things like
the BIOS tables etc).
Going back to that doesn't sound horrible.
Linus
next prev parent reply other threads:[~2008-04-26 17:16 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-24 22:56 Ingo Molnar
2008-04-25 23:43 ` Linus Torvalds
2008-04-26 0:06 ` H. Peter Anvin
2008-04-26 1:12 ` Linus Torvalds
2008-04-26 8:56 ` Ingo Molnar
2008-04-26 16:54 ` Pallipadi, Venkatesh
2008-04-26 17:15 ` Linus Torvalds [this message]
2008-04-26 18:32 ` Venki Pallipadi
2008-04-26 19:07 ` [patch] x86, PAT: disable /dev/mem mmap RAM with PAT Ingo Molnar
2008-04-26 9:57 ` [git pull] x86 PAT changes Ingo Molnar
2008-04-26 13:40 ` Gabriel C
2008-04-26 14:42 ` Ingo Molnar
2008-04-26 15:37 ` Gabriel C
2008-04-26 15:41 ` Ingo Molnar
2008-04-26 16:43 ` Linus Torvalds
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