Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level with runtime-time

From	Juergen Gross <jgross@suse.com>
Newsgroups	linux.kernel
Subject	Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level with runtime-time
Date	2017-07-27 10:30 +0200
Message-ID	<u7Mlc-3KZ-9@gated-at.bofh.it> (permalink)
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On 26/07/17 18:43, Kirill A. Shutemov wrote:
> On Wed, Jul 26, 2017 at 09:28:16AM +0200, Juergen Gross wrote:
>> 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).
> 
> Hm. Okay.
> 
> Have you tried PVH?

Now I have. Its coming up.

> 
>> Doesn't build with X86_5LEVEL not configured:
>>
>>   AS      arch/x86/kernel/head_64.o
> 
> I've fixed the patch and split the patch into two parts: cleanup and
> re-enabling XEN_PV and XEN_PVH for X86_5LEVEL.
> 
> There's chance that I screw somthing up in clenaup part. Could you check
> that?

Not sure I'll manage to do this today. Stay tuned...


Juergen

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[PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level with runtime-time "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2017-07-18 16:20 +0200
  Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level  with runtime-time Juergen Gross <jgross@suse.com> - 2017-07-18 16:30 +0200
    Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level  with runtime-time "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-07-18 17:20 +0200
    Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level  with runtime-time "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2017-07-25 11:10 +0200
      Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level  with runtime-time Juergen Gross <jgross@suse.com> - 2017-07-26 09:30 +0200
        Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level  with runtime-time "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-07-26 18:50 +0200
          Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level  with runtime-time Juergen Gross <jgross@suse.com> - 2017-07-27 10:30 +0200

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