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From: Juergen Gross <jgross@suse.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Andi Kleen <ak@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Michal Hocko <mhocko@kernel.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level with runtime-time
Date: Wed, 26 Jul 2017 09:28:16 +0200	[thread overview]
Message-ID: <39cb1e36-f94e-32ea-c94a-2daddcbf3408@suse.com> (raw)
In-Reply-To: <20170725090538.26sbgb4npkztsqj3@black.fi.intel.com>

On 25/07/17 11:05, Kirill A. Shutemov wrote:
> On Tue, Jul 18, 2017 at 04:24:06PM +0200, Juergen Gross wrote:
>> Xen PV guests will never run with 5-level-paging enabled. So I guess you
>> can drop the complete if (IS_ENABLED(CONFIG_X86_5LEVEL)) {} block.
> 
> There is more code to drop from mmu_pv.c.
> 
> But while there, I thought if with boot-time 5-level paging switching we
> can allow kernel to compile with XEN_PV and XEN_PVH, so the kernel image
> can be used in these XEN modes with 4-level paging.
> 
> Could you check if with the patch below we can boot in XEN_PV and XEN_PVH
> modes?

We can't. I have used your branch:

git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git
la57/boot-switching/v2

with this patch applied on top.

Doesn't boot PV guest with X86_5LEVEL configured (very early crash).
Doesn't build with X86_5LEVEL not configured:

  AS      arch/x86/kernel/head_64.o
/home/gross/linux/arch/x86/kernel/head_64.S: Assembler messages:
/home/gross/linux/arch/x86/kernel/head_64.S:350: Error: attempt to move
.org backwards
/home/gross/linux/arch/x86/kernel/head_64.S:352: Error: attempt to move
.org backwards
/home/gross/linux/arch/x86/kernel/head_64.S:43: Error: invalid operands
(*ABS* and *UND* sections) for `>>'
/home/gross/linux/arch/x86/kernel/head_64.S:44: Error: invalid operands
(*ABS* and *UND* sections) for `>>'
/home/gross/linux/scripts/Makefile.build:403: recipe for target
'arch/x86/kernel/head_64.o' failed
make[7]: *** [arch/x86/kernel/head_64.o] Error 1


Juergen

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  reply	other threads:[~2017-07-26  7:28 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-18 14:15 [PATCHv2 00/10] Boot-time switching between 4- and 5-level paging Kirill A. Shutemov
2017-07-18 14:15 ` [PATCHv2 01/10] x86/kasan: Use the same shadow offset for " Kirill A. Shutemov
2017-07-18 14:15 ` [PATCHv2 02/10] x86/xen: Provide pre-built page tables only for XEN_PV and XEN_PVH Kirill A. Shutemov
2017-07-18 14:15 ` [PATCHv2 03/10] x86/boot/compressed/64: Detect and handle 5-level paging at boot-time Kirill A. Shutemov
2017-07-18 14:15 ` [PATCHv2 04/10] x86/mm: Make virtual memory layout movable for CONFIG_X86_5LEVEL Kirill A. Shutemov
2017-07-18 14:15 ` [PATCHv2 05/10] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable Kirill A. Shutemov
2017-07-18 14:15 ` [PATCHv2 06/10] x86/mm: Handle boot-time paging mode switching at early boot Kirill A. Shutemov
2017-07-18 14:15 ` [PATCHv2 07/10] x86/mm: Fold p4d page table layer at runtime Kirill A. Shutemov
2017-07-18 14:15 ` [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level with runtime-time Kirill A. Shutemov
2017-07-18 14:24   ` Juergen Gross
2017-07-18 15:16     ` Kirill A. Shutemov
2017-07-25  9:05     ` Kirill A. Shutemov
2017-07-26  7:28       ` Juergen Gross [this message]
2017-07-26 16:43         ` Kirill A. Shutemov
2017-07-27  8:27           ` Juergen Gross
2017-08-01  7:46           ` Juergen Gross
2017-08-01 14:44             ` Kirill A. Shutemov
2017-08-01 17:14               ` Juergen Gross
2017-08-01 19:11                 ` Kirill A. Shutemov
2017-08-02  7:44                   ` Juergen Gross
2017-08-02  8:17                     ` Kirill A. Shutemov
2017-08-02  8:30                       ` Juergen Gross
2017-07-18 14:15 ` [PATCHv2 09/10] x86/mm: Allow to boot without la57 if CONFIG_X86_5LEVEL=y Kirill A. Shutemov
2017-07-18 14:15 ` [PATCHv2 10/10] x86/mm: Offset boot-time paging mode switching cost Kirill A. Shutemov

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