From: "H. Peter Anvin" <hpa@zytor.com>
To: Vivek Goyal <vgoyal@redhat.com>, Greg KH <greg@kroah.com>
Cc: mjg59@srcf.ucam.org, kexec@lists.infradead.org,
linux-kernel@vger.kernel.org, ebiederm@xmission.com
Subject: Re: [PATCH 5/6] kexec-bzImage: Support for loading bzImage using 64bit entry
Date: Fri, 22 Nov 2013 07:24:37 -0800 [thread overview]
Message-ID: <528F7735.9010209@zytor.com> (raw)
In-Reply-To: <20131121192114.GN16208@redhat.com>
On 11/21/2013 11:21 AM, Vivek Goyal wrote:
>>
>> What do you mean by the "real mode entry"? Do we need to care about
>> that because we aren't falling back to real mode when executing this,
>> are we? Or does that just happen for 32bit kernels?
>
> Original kexec offers real mode entry choice too. So we fall back
> to real mode and jump to kernel and kernel makes bunch of BIOS calls. I
> don't think this is a commonly used option.
>
I know some users of it (who I shall not name.) In general it is a bad
option, because after running the first kernel the state of the hardware
is not guaranteed to be such that executing the BIOS is safe. In
general, I do think they do it just because they tried at some point and
it happened to work; discouraging its use is probably for the better.
-hpa
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WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa@zytor.com>
To: Vivek Goyal <vgoyal@redhat.com>, Greg KH <greg@kroah.com>
Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
ebiederm@xmission.com, mjg59@srcf.ucam.org
Subject: Re: [PATCH 5/6] kexec-bzImage: Support for loading bzImage using 64bit entry
Date: Fri, 22 Nov 2013 07:24:37 -0800 [thread overview]
Message-ID: <528F7735.9010209@zytor.com> (raw)
In-Reply-To: <20131121192114.GN16208@redhat.com>
On 11/21/2013 11:21 AM, Vivek Goyal wrote:
>>
>> What do you mean by the "real mode entry"? Do we need to care about
>> that because we aren't falling back to real mode when executing this,
>> are we? Or does that just happen for 32bit kernels?
>
> Original kexec offers real mode entry choice too. So we fall back
> to real mode and jump to kernel and kernel makes bunch of BIOS calls. I
> don't think this is a commonly used option.
>
I know some users of it (who I shall not name.) In general it is a bad
option, because after running the first kernel the state of the hardware
is not guaranteed to be such that executing the BIOS is safe. In
general, I do think they do it just because they tried at some point and
it happened to work; discouraging its use is probably for the better.
-hpa
next prev parent reply other threads:[~2013-11-22 15:25 UTC|newest]
Thread overview: 180+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-20 17:50 [PATCH 0/6] kexec: A new system call to allow in kernel loading Vivek Goyal
2013-11-20 17:50 ` Vivek Goyal
2013-11-20 17:50 ` [PATCH 1/6] kexec: Export vmcoreinfo note size properly Vivek Goyal
2013-11-20 17:50 ` Vivek Goyal
2013-11-21 18:59 ` Greg KH
2013-11-21 18:59 ` Greg KH
2013-11-21 19:08 ` Vivek Goyal
2013-11-21 19:08 ` Vivek Goyal
2013-11-20 17:50 ` [PATCH 2/6] kexec: Move segment verification code in a separate function Vivek Goyal
2013-11-20 17:50 ` Vivek Goyal
2013-11-20 17:50 ` [PATCH 3/6] resource: Provide new functions to walk through resources Vivek Goyal
2013-11-20 17:50 ` Vivek Goyal
2013-11-20 17:50 ` [PATCH 4/6] kexec: A new system call, kexec_file_load, for in kernel kexec Vivek Goyal
2013-11-20 17:50 ` Vivek Goyal
2013-11-21 19:03 ` Greg KH
2013-11-21 19:03 ` Greg KH
2013-11-21 19:06 ` Matthew Garrett
2013-11-21 19:06 ` Matthew Garrett
2013-11-21 19:13 ` Vivek Goyal
2013-11-21 19:13 ` Vivek Goyal
2013-11-21 19:19 ` Matthew Garrett
2013-11-21 19:19 ` Matthew Garrett
2013-11-21 19:24 ` Vivek Goyal
2013-11-21 19:24 ` Vivek Goyal
2013-11-22 18:57 ` Vivek Goyal
2013-11-22 18:57 ` Vivek Goyal
2013-11-23 3:39 ` Eric W. Biederman
2013-11-23 3:39 ` Eric W. Biederman
2013-11-25 16:39 ` Vivek Goyal
2013-11-25 16:39 ` Vivek Goyal
2013-11-26 12:23 ` Eric W. Biederman
2013-11-26 12:23 ` Eric W. Biederman
2013-11-26 14:27 ` Vivek Goyal
2013-11-26 14:27 ` Vivek Goyal
2013-12-19 12:54 ` Torsten Duwe
2013-12-19 12:54 ` Torsten Duwe
2013-12-20 14:19 ` Vivek Goyal
2013-12-20 14:19 ` Vivek Goyal
2013-12-20 23:11 ` Eric W. Biederman
2013-12-20 23:11 ` Eric W. Biederman
2013-12-20 23:20 ` Kees Cook
2013-12-20 23:20 ` Kees Cook
2013-12-21 11:38 ` Torsten Duwe
2013-12-21 11:38 ` Torsten Duwe
2014-01-02 20:39 ` Vivek Goyal
2014-01-02 20:39 ` Vivek Goyal
2014-01-02 20:56 ` H. Peter Anvin
2014-01-02 20:56 ` H. Peter Anvin
2014-01-06 21:33 ` Josh Boyer
2014-01-06 21:33 ` Josh Boyer
2014-01-07 4:22 ` H. Peter Anvin
2014-01-07 4:22 ` H. Peter Anvin
2013-12-20 23:20 ` H. Peter Anvin
2013-12-20 23:20 ` H. Peter Anvin
2013-12-21 1:32 ` Eric W. Biederman
2013-12-21 1:32 ` Eric W. Biederman
2013-12-21 3:32 ` H. Peter Anvin
2013-12-21 3:32 ` H. Peter Anvin
2013-12-21 12:15 ` Torsten Duwe
2013-12-21 12:15 ` Torsten Duwe
2013-11-21 19:16 ` Vivek Goyal
2013-11-21 19:16 ` Vivek Goyal
2013-11-22 1:03 ` Kees Cook
2013-11-22 1:03 ` Kees Cook
2013-11-22 2:13 ` Vivek Goyal
2013-11-22 2:13 ` Vivek Goyal
2013-11-22 20:42 ` Jiri Kosina
2013-11-22 20:42 ` Jiri Kosina
2014-01-17 19:17 ` Vivek Goyal
2014-01-17 19:17 ` Vivek Goyal
2013-11-29 3:10 ` Baoquan He
2013-11-29 3:10 ` Baoquan He
2013-12-02 15:27 ` WANG Chao
2013-12-02 15:27 ` WANG Chao
2013-12-02 15:44 ` Vivek Goyal
2013-12-02 15:44 ` Vivek Goyal
2013-12-04 1:35 ` Baoquan He
2013-12-04 1:35 ` Baoquan He
2013-12-04 17:19 ` Vivek Goyal
2013-12-04 17:19 ` Vivek Goyal
2013-12-04 1:56 ` Baoquan He
2013-12-04 1:56 ` Baoquan He
2013-12-04 8:19 ` Baoquan He
2013-12-04 8:19 ` Baoquan He
2013-12-04 17:32 ` Vivek Goyal
2013-12-04 17:32 ` Vivek Goyal
2013-11-20 17:50 ` [PATCH 5/6] kexec-bzImage: Support for loading bzImage using 64bit entry Vivek Goyal
2013-11-20 17:50 ` Vivek Goyal
2013-11-21 19:07 ` Greg KH
2013-11-21 19:07 ` Greg KH
2013-11-21 19:21 ` Vivek Goyal
2013-11-21 19:21 ` Vivek Goyal
2013-11-22 15:24 ` H. Peter Anvin [this message]
2013-11-22 15:24 ` H. Peter Anvin
2013-11-28 11:35 ` Baoquan He
2013-11-28 11:35 ` Baoquan He
2013-12-02 15:36 ` Vivek Goyal
2013-12-02 15:36 ` Vivek Goyal
2013-11-20 17:50 ` [PATCH 6/6] kexec: Support for Kexec on panic using new system call Vivek Goyal
2013-11-20 17:50 ` Vivek Goyal
2013-11-28 11:28 ` Baoquan He
2013-11-28 11:28 ` Baoquan He
2013-12-02 15:30 ` Vivek Goyal
2013-12-02 15:30 ` Vivek Goyal
2013-12-04 1:51 ` Baoquan He
2013-12-04 1:51 ` Baoquan He
2013-12-04 17:20 ` Vivek Goyal
2013-12-04 17:20 ` Vivek Goyal
2013-12-04 1:41 ` Baoquan He
2013-12-04 1:41 ` Baoquan He
2013-12-04 17:19 ` Vivek Goyal
2013-12-04 17:19 ` Vivek Goyal
2013-11-21 18:58 ` [PATCH 0/6] kexec: A new system call to allow in kernel loading Greg KH
2013-11-21 18:58 ` Greg KH
2013-11-21 19:07 ` Vivek Goyal
2013-11-21 19:07 ` Vivek Goyal
2013-11-21 19:46 ` Vivek Goyal
2013-11-21 19:46 ` Vivek Goyal
2013-11-21 19:06 ` Geert Uytterhoeven
2013-11-21 19:06 ` Geert Uytterhoeven
2013-11-21 19:14 ` Vivek Goyal
2013-11-21 19:14 ` Vivek Goyal
2013-11-21 23:07 ` Eric W. Biederman
2013-11-21 23:07 ` Eric W. Biederman
2013-11-22 1:28 ` H. Peter Anvin
2013-11-22 1:28 ` H. Peter Anvin
2013-11-22 2:35 ` Vivek Goyal
2013-11-22 2:35 ` Vivek Goyal
2013-11-22 2:40 ` H. Peter Anvin
2013-11-22 2:40 ` H. Peter Anvin
2013-11-22 1:55 ` Vivek Goyal
2013-11-22 1:55 ` Vivek Goyal
2013-11-22 9:09 ` Geert Uytterhoeven
2013-11-22 9:09 ` Geert Uytterhoeven
2013-11-22 13:30 ` Jiri Kosina
2013-11-22 13:30 ` Jiri Kosina
2013-11-22 13:46 ` Vivek Goyal
2013-11-22 13:46 ` Vivek Goyal
2013-11-22 13:50 ` Jiri Kosina
2013-11-22 13:50 ` Jiri Kosina
2013-11-22 15:33 ` Vivek Goyal
2013-11-22 15:33 ` Vivek Goyal
2013-11-22 17:45 ` Kees Cook
2013-11-22 17:45 ` Kees Cook
2013-11-22 13:43 ` Vivek Goyal
2013-11-22 13:43 ` Vivek Goyal
2013-11-22 15:25 ` Geert Uytterhoeven
2013-11-22 15:25 ` Geert Uytterhoeven
2013-11-22 15:33 ` Jiri Kosina
2013-11-22 15:33 ` Jiri Kosina
2013-11-22 15:57 ` Eric Paris
2013-11-22 15:57 ` Eric Paris
2013-11-22 16:04 ` Jiri Kosina
2013-11-22 16:04 ` Jiri Kosina
2013-11-22 16:08 ` Vivek Goyal
2013-11-22 16:08 ` Vivek Goyal
2013-11-22 13:34 ` Eric W. Biederman
2013-11-22 13:34 ` Eric W. Biederman
2013-11-22 14:19 ` Vivek Goyal
2013-11-22 14:19 ` Vivek Goyal
2013-11-22 19:48 ` Greg KH
2013-11-22 19:48 ` Greg KH
2013-11-23 3:23 ` Eric W. Biederman
2013-11-23 3:23 ` Eric W. Biederman
2013-12-04 19:34 ` Vivek Goyal
2013-12-04 19:34 ` Vivek Goyal
2013-12-05 4:10 ` Eric W. Biederman
2013-12-05 4:10 ` Eric W. Biederman
2013-11-25 10:04 ` Michael Holzheu
2013-11-25 10:04 ` Michael Holzheu
2013-11-25 15:36 ` Vivek Goyal
2013-11-25 15:36 ` Vivek Goyal
2013-11-25 16:15 ` Michael Holzheu
2013-11-25 16:15 ` Michael Holzheu
2013-11-22 0:55 ` HATAYAMA Daisuke
2013-11-22 0:55 ` HATAYAMA Daisuke
2013-11-22 2:03 ` Vivek Goyal
2013-11-22 2:03 ` Vivek Goyal
2013-12-03 13:23 ` Baoquan He
2013-12-03 13:23 ` Baoquan He
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