From: Linus Torvalds <torvalds@osdl.org>
To: Andrew Morton <akpm@osdl.org>
Cc: mbligh@aracnet.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, kmannth@us.ibm.com
Subject: Re: [Bugme-new] [Bug 2019] New: Bug from the mm subsystem involving X (fwd)
Date: Wed, 4 Feb 2004 17:29:04 -0800 (PST) [thread overview]
Message-ID: <Pine.LNX.4.58.0402041719300.2086@home.osdl.org> (raw)
In-Reply-To: <20040204165620.3d608798.akpm@osdl.org>
On Wed, 4 Feb 2004, Andrew Morton wrote:
>
> pfn_valid() could become quite expensive indeed, and it lies on super-duper
> hotpaths.
Yes. However, sometimes it is the only choice.
So it does need to be fixed, and if it ends up being a noticeable
perofmance problem, then we can look at the hot-paths one by one and see
if we can avoid using it. We probably can, most of the time.
> An alternative which is less conceptually clean but should work in this
> case is to mark all vma's which were created by /dev/mem mappings as VM_IO,
> and test that in remap_page_range().
Hmm.. Grepping for "pfn_valid()", I'm starting to suspect that yes, with a
VM_IO approach and a fixed virt_addr_valid(), there really aren't any
other uses.
(virt_addr_valid() is useful for debugging and for validation of untrusted
pointers, but pfn_valid() just isn't very good for it. Never really was:
it started out as an ugly hack, and it never got cleaned up. It should be
easily fixable with something _proper_).
Linus
WARNING: multiple messages have this Message-ID (diff)
From: Linus Torvalds <torvalds@osdl.org>
To: Andrew Morton <akpm@osdl.org>
Cc: mbligh@aracnet.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, kmannth@us.ibm.com
Subject: Re: [Bugme-new] [Bug 2019] New: Bug from the mm subsystem involving X (fwd)
Date: Wed, 4 Feb 2004 17:29:04 -0800 (PST) [thread overview]
Message-ID: <Pine.LNX.4.58.0402041719300.2086@home.osdl.org> (raw)
In-Reply-To: <20040204165620.3d608798.akpm@osdl.org>
On Wed, 4 Feb 2004, Andrew Morton wrote:
>
> pfn_valid() could become quite expensive indeed, and it lies on super-duper
> hotpaths.
Yes. However, sometimes it is the only choice.
So it does need to be fixed, and if it ends up being a noticeable
perofmance problem, then we can look at the hot-paths one by one and see
if we can avoid using it. We probably can, most of the time.
> An alternative which is less conceptually clean but should work in this
> case is to mark all vma's which were created by /dev/mem mappings as VM_IO,
> and test that in remap_page_range().
Hmm.. Grepping for "pfn_valid()", I'm starting to suspect that yes, with a
VM_IO approach and a fixed virt_addr_valid(), there really aren't any
other uses.
(virt_addr_valid() is useful for debugging and for validation of untrusted
pointers, but pfn_valid() just isn't very good for it. Never really was:
it started out as an ugly hack, and it never got cleaned up. It should be
easily fixable with something _proper_).
Linus
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next prev parent reply other threads:[~2004-02-05 1:29 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-04 23:17 [Bugme-new] [Bug 2019] New: Bug from the mm subsystem involving X (fwd) Martin J. Bligh
2004-02-04 23:17 ` Martin J. Bligh
2004-02-04 23:58 ` Linus Torvalds
2004-02-04 23:58 ` Linus Torvalds
2004-02-05 0:12 ` Martin J. Bligh
2004-02-05 0:12 ` Martin J. Bligh
2004-02-05 0:36 ` Martin J. Bligh
2004-02-05 0:36 ` Martin J. Bligh
2004-02-05 0:43 ` Linus Torvalds
2004-02-05 0:43 ` Linus Torvalds
2004-02-05 0:56 ` Andrew Morton
2004-02-05 0:56 ` Andrew Morton
2004-02-05 1:29 ` Linus Torvalds [this message]
2004-02-05 1:29 ` Linus Torvalds
2004-02-05 1:56 ` Keith Mannthey
2004-02-05 1:56 ` Keith Mannthey
2004-02-05 2:04 ` Linus Torvalds
2004-02-05 2:04 ` Linus Torvalds
2004-02-05 2:33 ` Keith Mannthey
2004-02-05 2:33 ` Keith Mannthey
2004-02-05 2:47 ` Linus Torvalds
2004-02-05 2:47 ` Linus Torvalds
2004-02-06 7:17 ` Martin J. Bligh
2004-02-06 7:17 ` Martin J. Bligh
2004-02-06 7:19 ` Martin J. Bligh
2004-02-06 7:19 ` Martin J. Bligh
2004-02-06 9:57 ` Dave Hansen
2004-02-06 9:57 ` Dave Hansen
2004-02-06 15:49 ` Martin J. Bligh
2004-02-06 15:49 ` Martin J. Bligh
2004-02-06 17:22 ` Dave Hansen
2004-02-06 17:22 ` Dave Hansen
2004-02-06 19:59 ` Martin J. Bligh
2004-02-06 19:59 ` Martin J. Bligh
2004-02-06 20:16 ` Linus Torvalds
2004-02-06 20:16 ` Linus Torvalds
2004-02-06 21:18 ` Martin J. Bligh
2004-02-06 21:18 ` Martin J. Bligh
[not found] <51080000.1075936626@flay.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.58.0402041539470.2086@home.osdl.org.suse.lists.linux.kernel>
[not found] ` <60330000.1075939958@flay.suse.lists.linux.kernel>
[not found] ` <64260000.1075941399@flay.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.58.0402041639420.2086@home.osdl.org.suse.lists.linux.kernel>
[not found] ` <20040204165620.3d608798.akpm@osdl.org.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.58.0402041719300.2086@home.osdl.org.suse.lists.linux.kernel>
[not found] ` <1075946211.13163.18962.camel@dyn318004bld.beaverton.ibm.com.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.58.0402041800320.2086@home.osdl.org.suse.lists.linux.kernel>
[not found] ` <98220000.1076051821@[10.10.2.4].suse.lists.linux.kernel>
[not found] ` <1076061476.27855.1144.camel@nighthawk.suse.lists.linux.kernel>
[not found] ` <5450000.1076082574@[10.10.2.4].suse.lists.linux.kernel>
[not found] ` <1076088169.29478.2928.camel@nighthawk.suse.lists.linux.kernel>
[not found] ` <218650000.1076097590@flay.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.58.0402061215030.30672@home.osdl.org.suse.lists.linux.kernel>
[not found] ` <220850000.1076102320@flay.suse.lists.linux.kernel>
2004-02-07 3:54 ` Andi Kleen
2004-02-07 4:49 ` Martin J. Bligh
2004-02-07 5:21 ` Andi Kleen
2004-02-07 6:37 ` Nick Piggin
2004-02-07 7:31 ` Martin J. Bligh
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