All of lore.kernel.org
 help / color / mirror / Atom feed
From: Baoquan He <bhe@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	mingo@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	x86@kernel.org, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com
Subject: Re: [PATCH 1/3] x86/boot: Add bit fields into xloadflags for 5-level kernel checking
Date: Wed, 26 Sep 2018 15:54:33 +0800	[thread overview]
Message-ID: <20180926075433.GD2555@MiWiFi-R3L-srv> (raw)
In-Reply-To: <alpine.DEB.2.21.1809051002020.1416@nanos.tec.linutronix.de>

On 09/05/18 at 10:02am, Thomas Gleixner wrote:
> On Tue, 4 Sep 2018, H. Peter Anvin wrote:
> 
> > On 09/04/18 01:42, Kirill A. Shutemov wrote:
> > > 
> > > Switching between 4- and 5-level paging modes (in either direction)
> > > requires paing disabling. It means the code that does the switching has to
> > > be under 4G otherwise we would lose control.
> > > 
> > > We handle the switching correctly in kernel decompression code, but not on
> > > kexec caller side.
> > > 
> > > XLF_5LEVEL indicates that kernel decompression code can deal with
> > > switching between paging modes and it's safe to jump there in 5-level
> > > paging mode.
> > > 
> > > As an alternative we can change kexec to switch to 4-level paging mode
> > > before starting the new kernel. Not sure how hard it will be.
> > > 
> > 
> > Have a flag saying entering in 5-level mode is fine.  However, you really
> > should support returning to 4-level mode in kexec.  It is *much* easier to do
> > on the caller side as you have total control of memory allocation there.
> 
> Works for a regular kexec, but not for starting a crash kernel....

Agree, it's not appropriate to do this after normal kernel crashed and
prepare to jump to 2nd kernel.

Can this patchset be merged? I will post patches to kexec-tools utility
since it will make use of these flags.

Thanks
Baoquan

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

WARNING: multiple messages have this Message-ID (diff)
From: Baoquan He <bhe@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	mingo@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	x86@kernel.org, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com
Subject: Re: [PATCH 1/3] x86/boot: Add bit fields into xloadflags for 5-level kernel checking
Date: Wed, 26 Sep 2018 15:54:33 +0800	[thread overview]
Message-ID: <20180926075433.GD2555@MiWiFi-R3L-srv> (raw)
In-Reply-To: <alpine.DEB.2.21.1809051002020.1416@nanos.tec.linutronix.de>

On 09/05/18 at 10:02am, Thomas Gleixner wrote:
> On Tue, 4 Sep 2018, H. Peter Anvin wrote:
> 
> > On 09/04/18 01:42, Kirill A. Shutemov wrote:
> > > 
> > > Switching between 4- and 5-level paging modes (in either direction)
> > > requires paing disabling. It means the code that does the switching has to
> > > be under 4G otherwise we would lose control.
> > > 
> > > We handle the switching correctly in kernel decompression code, but not on
> > > kexec caller side.
> > > 
> > > XLF_5LEVEL indicates that kernel decompression code can deal with
> > > switching between paging modes and it's safe to jump there in 5-level
> > > paging mode.
> > > 
> > > As an alternative we can change kexec to switch to 4-level paging mode
> > > before starting the new kernel. Not sure how hard it will be.
> > > 
> > 
> > Have a flag saying entering in 5-level mode is fine.  However, you really
> > should support returning to 4-level mode in kexec.  It is *much* easier to do
> > on the caller side as you have total control of memory allocation there.
> 
> Works for a regular kexec, but not for starting a crash kernel....

Agree, it's not appropriate to do this after normal kernel crashed and
prepare to jump to 2nd kernel.

Can this patchset be merged? I will post patches to kexec-tools utility
since it will make use of these flags.

Thanks
Baoquan

  reply	other threads:[~2018-09-26  7:54 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-29 14:16 [PATCH 0/3] Add restrictions for kexec/kdump jumping between 5-level and 4-level kernel Baoquan He
2018-08-29 14:16 ` Baoquan He
2018-08-29 14:16 ` [PATCH 1/3] x86/boot: Add bit fields into xloadflags for 5-level kernel checking Baoquan He
2018-08-29 14:16   ` Baoquan He
2018-09-04  2:41   ` H. Peter Anvin
2018-09-04  2:41     ` H. Peter Anvin
2018-09-04  3:44     ` Baoquan He
2018-09-04  3:44       ` Baoquan He
2018-09-04  4:13       ` H. Peter Anvin
2018-09-04  4:13         ` H. Peter Anvin
2018-09-04  5:20         ` Baoquan He
2018-09-04  5:20           ` Baoquan He
2018-09-04  5:46           ` H. Peter Anvin
2018-09-04  5:46             ` H. Peter Anvin
2018-09-04  6:06             ` Baoquan He
2018-09-04  6:06               ` Baoquan He
2018-09-04  6:36               ` H. Peter Anvin
2018-09-04  6:36                 ` H. Peter Anvin
2018-09-04  7:16                 ` Baoquan He
2018-09-04  7:16                   ` Baoquan He
2018-09-04  8:42             ` Kirill A. Shutemov
2018-09-04  8:42               ` Kirill A. Shutemov
2018-09-05  4:06               ` H. Peter Anvin
2018-09-05  4:06                 ` H. Peter Anvin
2018-09-05  8:02                 ` Thomas Gleixner
2018-09-05  8:02                   ` Thomas Gleixner
2018-09-26  7:54                   ` Baoquan He [this message]
2018-09-26  7:54                     ` Baoquan He
2018-08-29 14:16 ` [PATCH 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel Baoquan He
2018-08-29 14:16   ` Baoquan He
2018-08-29 14:16 ` [PATCH 3/3] x86/kdump/64: Change the upper limit of crashkernel reservation Baoquan He
2018-08-29 14:16   ` Baoquan He
2018-08-30 13:50   ` Kirill A. Shutemov
2018-08-30 13:50     ` Kirill A. Shutemov
2018-08-30 14:13     ` Baoquan He
2018-08-30 14:13       ` Baoquan He
2018-08-30 13:58 ` [PATCH 0/3] Add restrictions for kexec/kdump jumping between 5-level and 4-level kernel Kirill A. Shutemov
2018-08-30 13:58   ` Kirill A. Shutemov
2018-08-30 14:12   ` Baoquan He
2018-08-30 14:12     ` Baoquan He
2018-08-30 14:27     ` Kirill A. Shutemov
2018-08-30 14:27       ` Kirill A. Shutemov
2018-08-30 14:57       ` Baoquan He
2018-08-30 14:57         ` Baoquan He
2018-08-30 15:01         ` Baoquan He
2018-08-30 15:01           ` Baoquan He
2018-09-02 20:45         ` Kirill A. Shutemov
2018-09-02 20:45           ` Kirill A. Shutemov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180926075433.GD2555@MiWiFi-R3L-srv \
    --to=bhe@redhat.com \
    --cc=hpa@zytor.com \
    --cc=kexec@lists.infradead.org \
    --cc=kirill.shutemov@linux.intel.com \
    --cc=kirill@shutemov.name \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.