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From: "H. Peter Anvin" <hpa@zytor.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vitaly Mayatskikh <v.mayatskih@gmail.com>,
	Cong Wang <amwang@redhat.com>,
	Neil Horman <nhorman@tuxdriver.com>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	Haren Myneni <hbabu@us.ibm.com>, Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH 0/5] Add second memory region for crash kernel
Date: Thu, 22 Apr 2010 15:37:53 -0700	[thread overview]
Message-ID: <4BD0CFC1.2060907@zytor.com> (raw)
In-Reply-To: <m1aasvkupc.fsf@fess.ebiederm.org>

On 04/22/2010 03:07 PM, Eric W. Biederman wrote:
> 
> Have you tried loading a 64bit vmlinux directly into a higher address
> range?  There may be a bit or two missing but you should be able to
> load a linux kernel above 4GB.  I tested the basics of that mechanism
> when I made the 64bit relocatable kernel.
> 
> I don't buy the argument that there is a direct connection between
> the amount of memory you have and how much memory it takes to dump it.
> Even an indirect connections seems suspicious.
> 

We actually have a 64-bit entry point even in bzImage; it is at offset
+0x200 from the 32-bit entry point.  Right now that offset is not
exported anywhere, but it has been stable for a very long time... at
least for as far back as the decompressor has been 64 bits.

The interface to the 64-bit code is by necessity wider, since there is
no such thing as paging off in 64-bit mode, but it probably isn't *too*
hard to figure out how page tables need to be set up in order to work
properly.  At that point, it would be good to document it.

	-hpa

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kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa@zytor.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vitaly Mayatskikh <v.mayatskih@gmail.com>,
	linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Vivek Goyal <vgoyal@redhat.com>,
	Haren Myneni <hbabu@us.ibm.com>,
	Neil Horman <nhorman@tuxdriver.com>,
	Cong Wang <amwang@redhat.com>,
	kexec@lists.infradead.org
Subject: Re: [PATCH 0/5] Add second memory region for crash kernel
Date: Thu, 22 Apr 2010 15:37:53 -0700	[thread overview]
Message-ID: <4BD0CFC1.2060907@zytor.com> (raw)
In-Reply-To: <m1aasvkupc.fsf@fess.ebiederm.org>

On 04/22/2010 03:07 PM, Eric W. Biederman wrote:
> 
> Have you tried loading a 64bit vmlinux directly into a higher address
> range?  There may be a bit or two missing but you should be able to
> load a linux kernel above 4GB.  I tested the basics of that mechanism
> when I made the 64bit relocatable kernel.
> 
> I don't buy the argument that there is a direct connection between
> the amount of memory you have and how much memory it takes to dump it.
> Even an indirect connections seems suspicious.
> 

We actually have a 64-bit entry point even in bzImage; it is at offset
+0x200 from the 32-bit entry point.  Right now that offset is not
exported anywhere, but it has been stable for a very long time... at
least for as far back as the decompressor has been 64 bits.

The interface to the 64-bit code is by necessity wider, since there is
no such thing as paging off in 64-bit mode, but it probably isn't *too*
hard to figure out how page tables need to be set up in order to work
properly.  At that point, it would be good to document it.

	-hpa

  reply	other threads:[~2010-04-22 22:41 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-04-22 16:23 [PATCH 0/5] Add second memory region for crash kernel Vitaly Mayatskikh
2010-04-22 16:23 ` Vitaly Mayatskikh
2010-04-22 16:23 ` [PATCH 1/5] Introduce second memory resource " Vitaly Mayatskikh
2010-04-22 16:23   ` Vitaly Mayatskikh
2010-04-22 16:23 ` [PATCH 2/5] Modify parse_crashkernel* for new syntax Vitaly Mayatskikh
2010-04-22 16:23   ` Vitaly Mayatskikh
2010-04-22 16:23 ` [PATCH 3/5] Support second memory region in crash_shrink_memory() Vitaly Mayatskikh
2010-04-22 16:23   ` Vitaly Mayatskikh
2010-04-22 16:23 ` [PATCH 4/5] x86: use second memory region for dump-capture kernel Vitaly Mayatskikh
2010-04-22 16:23   ` Vitaly Mayatskikh
2010-04-22 16:23 ` [PATCH 5/5] kexec: update documentation Vitaly Mayatskikh
2010-04-22 16:23   ` Vitaly Mayatskikh
2010-04-22 22:07 ` [PATCH 0/5] Add second memory region for crash kernel Eric W. Biederman
2010-04-22 22:07   ` Eric W. Biederman
2010-04-22 22:37   ` H. Peter Anvin [this message]
2010-04-22 22:37     ` H. Peter Anvin
2010-04-22 22:45   ` Vivek Goyal
2010-04-22 22:45     ` Vivek Goyal
2010-04-23  0:48     ` Eric W. Biederman
2010-04-23  0:48       ` Eric W. Biederman
2010-04-23  5:21       ` Cong Wang
2010-04-23  5:21         ` Cong Wang
2010-04-23  5:42         ` Eric W. Biederman
2010-04-23  5:42           ` Eric W. Biederman
2010-04-23  6:43           ` Vitaly Mayatskikh
2010-04-23  6:43             ` Vitaly Mayatskikh
2010-04-23 14:44       ` Vivek Goyal
2010-04-23 14:44         ` Vivek Goyal
2010-04-23  7:08     ` Vitaly Mayatskikh
2010-04-23  7:08       ` Vitaly Mayatskikh

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