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From: Pekka Paalanen <pq@iki.fi>
To: Ingo Molnar <mingo@elte.hu>
Cc: Arjan van de Ven <arjan@infradead.org>,
	Harvey Harrison <harvey.harrison@gmail.com>,
	linux-kernel@vger.kernel.org, Jan Beulich <jbeulich@novell.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Pavel Roskin <proski@gnu.org>
Subject: Re: [PATCH v2] x86: Add a list for custom page fault handlers.
Date: Sun, 3 Feb 2008 23:40:11 +0200	[thread overview]
Message-ID: <20080203234011.5f18ad21@daedalus.pq.iki.fi> (raw)
In-Reply-To: <20080203070321.GA8293@elte.hu>

On Sun, 3 Feb 2008 08:03:21 +0100
Ingo Molnar <mingo@elte.hu> wrote:

> i dont think this second problem is a practical one: i've test-merged 
> mmiotrace two days ago into x86.git and it's holding up very well in my 
> testing (it has not caused a single hickup so far). It's nice optional 
> debug functionality and i dont see any reason why not to merge it.

Good to hear!

I've made some fixes since my last mmiotrace patch (v2). Rewritten things
to use lookup_address(), added EXPORT_SYMBOL(lookup_address) into
pageattr.c to make it work (this hopefully fixed the undefined symbol
'init_mm' on x86-32), and fixed relay-buffer-full flags on SMP.

> a few cleanup requests:
> 
> - please make the pagefault callbacks explicit as Arjan has asked

What does this mean in practice? It should be able to call into a module,
so the only thing I can come up with is a single settable function
pointer. Just like I proposed in patch v2, but a function pointer instead
of a list. Is this what you and Arjan suggest?
We are talking about the hook in do_page_fault(), right?

> - any reason why it lives in arch/x86/kernel/mmiotrace/? It should be a
>   prime-time member of arch/x86/mm/ i think.

I was waiting for someone to comment on that, I didn't know what was the
proper place. I'll move it into there.

> - please make it build-in-able, not modules-only.

Then I need a way to clear the relay buffers at some point. Currently
they get cleared only on module unload. Maybe preferably also allocate
and deallocate them dynamically. I've no idea how to do this yet, any
pointers to examples?

Hmm, I guess relay buffers could be allocated on the first intercepted
call to ioremap, but then the userspace could not be started before
hand, and at that point it is too late.

Making it build-in-able will take so much time that I'd prefer to aim
it for 2.6.26.

> - [ longer-term: think about integrating pf_in.c with the x86
>     emulator/disassembler of KVM. ]

Yikes. Like I replied to Arjan, it looks daunting.


Thanks, I'll do what I can. When do you need the final (as for 2.6.25)
mmiotrace patch, or is it going in as v2 and then we fix it in RCs?

-- 
Pekka Paalanen
http://www.iki.fi/pq/

  reply	other threads:[~2008-02-03 21:40 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-27 16:52 [PATCH] " Pekka Paalanen
2008-01-27 17:55 ` [RFC PATCH] x86: mmiotrace - trace memory mapped IO Pekka Paalanen
2008-01-30 22:39   ` Pekka Paalanen
2008-01-27 19:29 ` [PATCH] x86: Add a list for custom page fault handlers Ingo Molnar
2008-01-27 21:03 ` Peter Zijlstra
2008-01-30  2:28 ` Harvey Harrison
2008-01-30  2:34   ` Harvey Harrison
2008-01-30 18:08     ` Pekka Paalanen
2008-01-31 15:07       ` Ingo Molnar
2008-01-31 16:02         ` [PATCH v2] " Pekka Paalanen
2008-01-31 16:15           ` Arjan van de Ven
2008-02-03  6:55             ` Pekka Paalanen
2008-02-03  7:03               ` Ingo Molnar
2008-02-03 21:40                 ` Pekka Paalanen [this message]
2008-02-05 20:28                 ` [PATCH 1/4] x86 mmiotrace: use lookup_address() Pekka Paalanen
2008-02-05 20:30                   ` [PATCH 2/4] x86 mmiotrace: fix relay-buffer-full flag for SMP Pekka Paalanen
2008-02-05 20:44                     ` Eric Dumazet
2008-02-05 21:14                       ` Pekka Paalanen
2008-02-05 21:35                         ` Eric Dumazet
2008-02-09 17:53                           ` [PATCH] x86 mmiotrace: Use percpu instead of arrays Pekka Paalanen
2008-02-05 20:31                   ` [PATCH 3/4] x86 mmiotrace: comment about user space ABI Pekka Paalanen
2008-02-05 20:39                   ` [PATCH 4/4] x86 mmiotrace: move files into arch/x86/mm/ Pekka Paalanen
2008-02-06  3:02                     ` Randy Dunlap
2008-02-09 11:21                       ` Pekka Paalanen
2008-02-07 12:53                     ` Ingo Molnar
2008-02-07 12:56                       ` Christoph Hellwig
2008-02-09 17:52                         ` [RFC PATCH] x86: explicit call to mmiotrace in do_page_fault() Pekka Paalanen
2008-02-09 18:01                           ` Arjan van de Ven
2008-02-09 18:23                             ` Pekka Paalanen
2008-02-09 18:56                               ` Pekka Enberg
2008-02-09 19:11                                 ` Pekka Paalanen
2008-02-09 19:19                                   ` Pekka Enberg
2008-02-09 18:39                             ` Peter Zijlstra
2008-02-09 18:39                           ` Peter Zijlstra
2008-02-10 18:05                             ` [RFC PATCH v2] " Pekka Paalanen
2008-02-11  2:12                               ` Pavel Roskin
2008-02-11 18:04                                 ` Pekka Paalanen
2008-02-06  5:00                   ` [PATCH 1/4] x86 mmiotrace: use lookup_address() Christoph Hellwig
2008-02-07 12:52                     ` Ingo Molnar
2008-01-31 16:16           ` [RFC PATCH v2] x86: mmiotrace - trace memory mapped IO Pekka Paalanen
2008-01-31 16:29             ` Arjan van de Ven
2008-02-03  7:21               ` Pekka Paalanen
2008-01-30 18:20 ` [PATCH] x86: Add a list for custom page fault handlers Arjan van de Ven

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