Re: [PATCH] x86: fix {pmd,pud}_{set,clear}_flags()
From: Juergen Gross
Date: Mon Feb 19 2018 - 12:41:31 EST
On 19/02/18 18:04, Jan Beulich wrote:
>>>> On 19.02.18 at 17:23, <jgross@xxxxxxxx> wrote:
>> On 19/02/18 15:48, Jan Beulich wrote:
>>> Just like pte_{set,clear}_flags() their PMD and PUD counterparts should
>>> not do any address translation. This was outright wrong under Xen
>>> (causing a dead boot with no useful output on "suitable" systems), and
>>> produced needlessly more complicated code (even if just slightly) when
>>> paravirt was enabled.
>>>
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>> Cc: stable@xxxxxxxxxxxxxxx
>>
>> While the changes look alright I'm really curious which kind of failure
>> you are seeing, especially considering how long those functions haven't
>> been changed (since more than 6 years).
>
> It's the new use of pmd_set_flags() in 2cc42bac1c ("x86-64/Xen:
> eliminate W+X mappings"), and due to the (very odd afaic) identity
> map handling the issue is invisible on most systems/setups.
Aah, okay. This helps.
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Juergen