From: Baoquan He <bhe@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org, kexec@lists.infradead.org,
linux-kernel@vger.kernel.org, tglx@linutronix.de,
mingo@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: Tue, 4 Sep 2018 13:20:36 +0800 [thread overview]
Message-ID: <20180904052036.GJ1740@192.168.1.3> (raw)
In-Reply-To: <4546fc39-4982-4c91-c812-0df1e9bc9e20@zytor.com>
On 09/03/18 at 09:13pm, H. Peter Anvin wrote:
> On 09/03/18 20:44, Baoquan He wrote:
> >
> > 1) in arch/x86/kernel/relocate_kernel_64.S, we set X86_CR4_LA57 into cr4
> > if the 1st kernel is in 5-level mode. Then in
> > arch/x86/boot/compressed/head_64.S, paging_prepare() is called to decide
> > if 5-level mode will be enabled, and prepare the trampoline. If
> > kexec/kdump kernel is expected to be in 4-level, e.g with 'nolv5'
> > specified, it still can handle well. But for the old kernel w/o these
> > 5-level codes, it will ignore the fact that X86_CR4_LA57 has been set
> > in CR4 and proceed anyway, then #GP is triggered. That's why XLF_5LEVEL
> > is used to mark.
> >
>
> That's what I'm saying, don't do that. Always jump into the second kernel in
> 4-level mode, i.e. X86_CR4_LA57 unset. That's the only sane thing.
Well, this might not be suggested. Kexec has been a formal feature in
our distro, our customers usually use it to reboot high end servers
because those machines may take one hour to boot up from firmware. And
5-level may be also supported very soon, if people want to do a fast
reboot from the current kernel in 5-level, and expect to see it's in
5-level too in the 2nd kernel, this always kexec jumping to the 2nd
kernel in 4-level mode might be unaccepted.
Thanks
Baoquan
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next prev parent reply other threads:[~2018-09-04 5:20 UTC|newest]
Thread overview: 24+ 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 ` [PATCH 1/3] x86/boot: Add bit fields into xloadflags for 5-level kernel checking Baoquan He
2018-09-04 2:41 ` H. Peter Anvin
2018-09-04 3:44 ` Baoquan He
2018-09-04 4:13 ` H. Peter Anvin
2018-09-04 5:20 ` Baoquan He [this message]
2018-09-04 5:46 ` H. Peter Anvin
2018-09-04 6:06 ` Baoquan He
2018-09-04 6:36 ` H. Peter Anvin
2018-09-04 7:16 ` Baoquan He
2018-09-04 8:42 ` Kirill A. Shutemov
2018-09-05 4:06 ` H. Peter Anvin
2018-09-05 8:02 ` Thomas Gleixner
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 ` [PATCH 3/3] x86/kdump/64: Change the upper limit of crashkernel reservation Baoquan He
2018-08-30 13:50 ` Kirill A. Shutemov
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 14:12 ` Baoquan He
2018-08-30 14:27 ` Kirill A. Shutemov
2018-08-30 14:57 ` Baoquan He
2018-08-30 15:01 ` Baoquan He
2018-09-02 20:45 ` Kirill A. Shutemov
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