From: Andi Kleen <ak@linux.intel.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>,
the arch/x86 maintainers <x86@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@amacapital.net>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Borislav Petkov <bp@suse.de>, linux-mm <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCHv6, RESEND 4/4] x86/boot/compressed/64: Handle 5-level paging boot if kernel is above 4G
Date: Tue, 23 Jan 2018 10:13:35 -0800 [thread overview]
Message-ID: <20180123181335.GP7844@tassilo.jf.intel.com> (raw)
In-Reply-To: <20180123173703.rrr7igl7xtlsawhf@node.shutemov.name>
On Tue, Jan 23, 2018 at 08:37:03PM +0300, Kirill A. Shutemov wrote:
> On Tue, Jan 23, 2018 at 09:31:16AM -0800, Linus Torvalds wrote:
> > On Tue, Jan 23, 2018 at 9:09 AM, Kirill A. Shutemov
> > <kirill.shutemov@linux.intel.com> wrote:
> > >
> > > But if the bootloader put the kernel above 4G (not sure if anybody does
> > > this), we would lose control as soon as paging is disabled, because the
> > > code becomes unreachable to the CPU.
> >
> > I do wonder if we need this. Why would a bootloader ever put the data
> > above 4G? Does this really happen? Wouldn't it be easier to just say
> > "bootloaders better put the kernel in the low 4G"?
>
> I don't know much about bootloaders, but do we even have such guarantee
> for in-kernel bootloader -- kexec?
There's no such guarantee, so we need it at least for kexec.
-Andi
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prev parent reply other threads:[~2018-01-23 18:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-23 17:09 [PATCHv6, RESEND 0/4] x86: 5-level related changes into decompression code Kirill A. Shutemov
2018-01-23 17:09 ` [PATCHv6, RESEND 1/4] x86/boot/compressed/64: Rename pagetable.c to kaslr_64.c Kirill A. Shutemov
2018-01-23 17:09 ` [PATCHv6, RESEND 2/4] x86/boot/compressed/64: Introduce paging_prepare() Kirill A. Shutemov
2018-01-23 17:09 ` [PATCHv6, RESEND 3/4] x86/boot/compressed/64: Prepare trampoline memory Kirill A. Shutemov
2018-01-23 17:09 ` [PATCHv6, RESEND 4/4] x86/boot/compressed/64: Handle 5-level paging boot if kernel is above 4G Kirill A. Shutemov
2018-01-23 17:31 ` Linus Torvalds
2018-01-23 17:37 ` Kirill A. Shutemov
2018-01-23 18:13 ` Andi Kleen [this message]
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