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Re: [PATCH] xen: fix usage of pmd/pud_poplulate in mremap for pv guests

  • To: Juergen Gross <jgross@xxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Wed, 8 Sep 2021 16:28:14 +0200
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  • Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, stable@xxxxxxxxxxxxxxx, Sander Eikelenboom <linux@xxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
  • Delivery-date: Wed, 08 Sep 2021 14:28:27 +0000
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On 08.09.2021 15:32, Juergen Gross wrote:
> On 08.09.21 13:07, Jan Beulich wrote:
>> On 08.09.2021 09:36, Juergen Gross wrote:
>>> Commit 0881ace292b662 ("mm/mremap: use pmd/pud_poplulate to update page
>>> table entries") introduced a regression when running as Xen PV guest.
>> The description of that change starts with "pmd/pud_populate is the
>> right interface to be used to set the respective page table entries."
>> If this is deemed true, I don't think pmd_populate() should call
>> paravirt_alloc_pte(): The latter function, as its name says, is
>> supposed to be called for newly allocated page tables only (aiui).
> In theory you are correct, but my experience with reality tells me that
> another set of macros for this case will not be appreciated.

Perhaps a new parameter to the macros / inlines identifying fresh
vs moved? Or perhaps the offending change wasn't really correct in
what its description said?




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