linux-kernel - Re: [Xen-devel] [PATCH] xen: adjust early dom0 p2m handling to xen hypervisor behavior

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Date:   Wed, 10 May 2017 10:08:32 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Jan Beulich <JBeulich@...e.com>
Cc:     xen-devel@...ts.xenproject.org, boris.ostrovsky@...cle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] xen: adjust early dom0 p2m handling to xen
 hypervisor behavior

On 10/05/17 10:02, Jan Beulich wrote:
>>>> On 10.05.17 at 06:08, <jgross@...e.com> wrote:
>> When booted as pv-guest the p2m list presented by the Xen is already
>> mapped to virtual addresses. In dom0 case the hypervisor might make use
>> of 2M- or 1G-pages for this mapping. Unfortunately while being properly
>> aligned in virtual and machine address space, those pages might not be
>> aligned properly in guest physical address space.
>>
>> So when trying to obtain the guest physical address of such a page
>> pud_pfn() and pmd_pfn() must be avoided as those will mask away guest
>> physical address bits not being zero in this special case.
>>
>> Signed-off-by: Juergen Gross <jgross@...e.com>
> 
> Reviewed-by: Jan Beulich <jbeulich@...e.com>
> 
> Perhaps worth Cc-ing stable@ ?

Any backport needs to be done manually, as mmu_pv.c has been introduced
in 4.12 only.

As soon as the patch is upstream I'm planning to do that (trivial)
backport and send it to stable.


Juergen