linux-kernel - Re: [PATCH] x86/head: Refactor 32-bit pgtable setup

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Date:   Mon, 19 Dec 2016 09:09:13 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org, matt@...eblueprint.co.uk,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH] x86/head: Refactor 32-bit pgtable setup

On 12/18/2016 03:44 AM, Ingo Molnar wrote:
> * Boris Ostrovsky <boris.ostrovsky@...cle.com> wrote:
>
>> On 12/08/2016 11:33 PM, Ingo Molnar wrote:
>>> * Boris Ostrovsky <boris.ostrovsky@...cle.com> wrote:
>>>
>>>> The new Xen PVH entry point requires page tables to be setup by the
>>>> kernel since it is entered with paging disabled.
>>>>
>>>> Pull the common code out of head_32.S so that mk_early_pgtbl_32 can be
>>>> invoked from both the new Xen entry point and the existing startup_32
>>>> code.
>>>>
>>>> Convert resulting common code to C.
>>>>
>>>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
>>>> ---
>>>> This is replacement for https://lkml.org/lkml/2016/10/14/434, with
>>>> assembly code re-written in C as requested by Ingo.
>>>>
>>>>
>>>>  arch/x86/include/asm/pgtable_32.h |  32 ++++++++++
>>>>  arch/x86/kernel/head32.c          |  62 +++++++++++++++++++
>>>>  arch/x86/kernel/head_32.S         | 122 +++-----------------------------------
>>>>  3 files changed, 101 insertions(+), 115 deletions(-)
>>> Whee, I love it! And the code is so much more readable!
>>>
>>> Did you have any particular robustness problems (difficult to resolve crashes) 
>>> while developing it, or was it reasonably straightforward to do?
>> There was nothing particularly difficult beyond understanding current
>> code. That, of course, is not to say that there were no crashes but
>> developing this on a guest gives you pretty good insight into why/where
>> you crashed.
>>
>> This was tested on bare-metal (in case you are wondering), but obviously
>> more testing is always good.
> Ok, cool!
>
> Would you like to carry this with your other Xen dependencies? If yes:
>
>    Acked-by: Ingo Molnar <mingo@...nel.org>
>
> If not then I can pick it up and get it to Linus in v4.10.


I don't think my series will get into 4.10 since it is has a dependency
on hypervisor code that is still being reviewed.

If you could take it via your tree it would be great. Thanks!

-boris