From: Arnd Bergmann <arnd@arndb.de>
To: Oren Laadan <orenl@cs.columbia.edu>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>,
containers@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, Theodore Tso <tytso@mit.edu>,
"Serge E. Hallyn" <serue@us.ibm.com>
Subject: Re: [RFC][PATCH 2/4] checkpoint/restart: x86 support
Date: Sat, 9 Aug 2008 00:29:27 +0200 [thread overview]
Message-ID: <200808090029.28286.arnd@arndb.de> (raw)
In-Reply-To: <489CAC70.7090809@cs.columbia.edu>
On Friday 08 August 2008, Oren Laadan wrote:
> > It seems weird that you use __u64 members for the registers, but don't
> > include r8..r15 in the list. As a consequence, this structure does not
> > seem well suited for either x86-32 or x86-64.
>
> In the context of CR, x86-32 and x86-64 are distinct architectures because
> you cannot always migrate from one to the other (though 32->64 is sometimes
> possible). Therefore, each architecture can have a separate checkpoint file
> format (eg r8..r15 only for x86-64).
So why do you use __u64 members for your 32 bit registers?
> Except for this special case (32 bit running 64 bit), simple conversion can
> be done in the kernel if needed, but most conversion between kernel the
> format for different kernel versions (should it change) can be done in
> user space (eg. with a filter).
The 32bit on 64bit case is quite common on non-x86 architectures, e.g.
powerpc or sparc, where 64 bit kernels typically run 32 bit user space.
A particularly interesting case is mixing 32 and 64 bit tasks in a container
that you are checkpointing. This is a very realistic scenario, so there
may be good arguments for keeping the format identical between the variations
of each architecture.
> > I would suggest either using struct pt_regs by reference, or defining
> > it so that you can use the same structure for both 32 and 64 bit x86.
>
> We prefer not to use the kernel structure directly, but an intermediate
> structure that can help mitigate subtle incompatibilities issues (between
> kernel configurations, versions, and even compiler versions).
>
> Anyway, either a single structure for both 32 and 64 bit x86, or separate
> "struct cr_hdr_cpu{_32,_64}", one for each architecture.
struct pt_regs is part of the kernel ABI, it will not change.
Arnd <><
next prev parent reply other threads:[~2008-08-08 22:30 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-07 22:40 [RFC][PATCH 0/4] kernel-based checkpoint restart Dave Hansen
2008-08-07 22:40 ` [RFC][PATCH 1/4] checkpoint-restart: general infrastructure Dave Hansen
2008-08-08 9:46 ` Arnd Bergmann
2008-08-08 18:50 ` Dave Hansen
2008-08-08 20:59 ` Oren Laadan
2008-08-08 22:17 ` Dave Hansen
2008-08-08 23:27 ` Oren Laadan
2008-08-08 22:23 ` Arnd Bergmann
2008-08-14 8:09 ` [Devel] " Pavel Emelyanov
2008-08-14 15:16 ` Dave Hansen
2008-08-08 22:13 ` Arnd Bergmann
2008-08-08 22:26 ` Dave Hansen
2008-08-08 22:39 ` Arnd Bergmann
2008-08-09 0:43 ` Dave Hansen
2008-08-09 6:37 ` Arnd Bergmann
2008-08-09 13:39 ` Dave Hansen
2008-08-11 15:07 ` Serge E. Hallyn
2008-08-11 15:25 ` Arnd Bergmann
2008-08-14 5:53 ` Pavel Machek
2008-08-14 15:12 ` Dave Hansen
2008-08-20 21:40 ` Oren Laadan
2008-08-11 15:22 ` Serge E. Hallyn
2008-08-11 16:53 ` Arnd Bergmann
2008-08-11 17:11 ` Dave Hansen
2008-08-11 19:48 ` checkpoint/restart ABI Dave Hansen
2008-08-11 21:47 ` Arnd Bergmann
2008-08-11 23:14 ` Jonathan Corbet
2008-08-11 23:23 ` Dave Hansen
2008-08-21 5:56 ` Oren Laadan
2008-08-21 8:43 ` Arnd Bergmann
2008-08-21 15:43 ` Oren Laadan
2008-08-11 21:54 ` Oren Laadan
2008-08-11 23:38 ` Jeremy Fitzhardinge
2008-08-11 23:54 ` Peter Chubb
2008-08-12 14:49 ` Serge E. Hallyn
2008-08-28 23:40 ` Eric W. Biederman
2008-08-12 15:11 ` Dave Hansen
2008-08-12 14:58 ` Dave Hansen
2008-08-12 16:32 ` Jeremy Fitzhardinge
2008-08-12 16:46 ` Dave Hansen
2008-08-12 17:04 ` Jeremy Fitzhardinge
2008-08-20 21:52 ` Oren Laadan
2008-08-20 21:54 ` Oren Laadan
2008-08-20 22:11 ` Dave Hansen
2008-08-11 18:03 ` [RFC][PATCH 1/4] checkpoint-restart: general infrastructure Jonathan Corbet
2008-08-11 18:38 ` Dave Hansen
2008-08-12 3:44 ` Oren Laadan
2008-08-18 9:26 ` [Devel] " Pavel Emelyanov
2008-08-20 19:10 ` Dave Hansen
2008-08-07 22:40 ` [RFC][PATCH 2/4] checkpoint/restart: x86 support Dave Hansen
2008-08-08 12:09 ` Arnd Bergmann
2008-08-08 20:28 ` Oren Laadan
2008-08-08 22:29 ` Arnd Bergmann [this message]
2008-08-08 23:04 ` Oren Laadan
2008-08-09 0:38 ` Dave Hansen
2008-08-09 1:20 ` Oren Laadan
2008-08-09 2:20 ` Dave Hansen
2008-08-09 2:35 ` Oren Laadan
2008-08-10 14:55 ` Jeremy Fitzhardinge
2008-08-11 15:36 ` Dave Hansen
2008-08-11 16:07 ` Jeremy Fitzhardinge
2008-08-09 6:43 ` Arnd Bergmann
2008-08-07 22:40 ` [RFC][PATCH 3/4] checkpoint/restart: memory management Dave Hansen
2008-08-08 12:12 ` Arnd Bergmann
2008-08-07 22:40 ` [RFC][PATCH 4/4] introduce sys_checkpoint and sys_restore Dave Hansen
2008-08-08 12:15 ` Arnd Bergmann
2008-08-08 20:33 ` Oren Laadan
2008-08-08 9:25 ` [RFC][PATCH 0/4] kernel-based checkpoint restart Arnd Bergmann
2008-08-08 18:06 ` Dave Hansen
2008-08-08 18:18 ` Arnd Bergmann
2008-08-08 19:44 ` Oren Laadan
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