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From: Michael Ellerman <mpe@ellerman.id.au>
To: LEROY Christophe <christophe.leroy@c-s.fr>
Cc: aneesh.kumar@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 23/24] powerpc/mm: Cleanup check for stack expansion
Date: Tue, 25 Jul 2017 21:19:47 +1000	[thread overview]
Message-ID: <87379k7oh8.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20170724193402.Horde.6aHXbQVl2cfpW3l9leYB8Q2@messagerie.c-s.fr>

LEROY Christophe <christophe.leroy@c-s.fr> writes:

> Michael Ellerman <mpe@ellerman.id.au> a =C3=A9crit=C2=A0:
>
>> LEROY Christophe <christophe.leroy@c-s.fr> writes:
>>
>>> Benjamin Herrenschmidt <benh@kernel.crashing.org> a =C3=A9crit=C2=A0:
>>>
>>>> When hitting below a VM_GROWSDOWN vma (typically growing the stack),
>>>> we check whether it's a valid stack-growing instruction and we
>>>> check the distance to GPR1. This is largely open coded with lots
>>>> of comments, so move it out to a helper.
>>>
>>> Did you have a look at the following patch ? It's been waiting for
>>> application for some weeks now.
>>> https://patchwork.ozlabs.org/patch/771869
>>
>> I actually merged it last merge window, but found I had no good way to
>> test it, so I took it out again until I can write a test case for it.
>>
>> The way I realised it wasn't being tested was by removing all the
>> store_updates_sp logic entirely and having my system run happily for
>> several days :}
>
> Which demonstrates how unlikely this is, hence doing that get_user()=20=20
> at every fault is waste of time.

Yes I agree.

> How do you plan to handle that in parralele to ben's serie ?

Not sure :)

> I'll be back from vacation next week and may help finding a way to=20=20
> test that. (A test program using alloca() ?)

I was thinking hand-crafted asm, but that might be a pain to get working
for 32 & 64-bit, in which case alloca() might work.

cheers

  reply	other threads:[~2017-07-25 11:19 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-19  4:49 [PATCH 01/24] powerpc/mm: Move exception_enter/exit to a do_page_fault wrapper Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 02/24] powerpc/mm: Pre-filter SRR1 bits before do_page_fault() Benjamin Herrenschmidt
2017-07-22 16:43   ` LEROY Christophe
2017-07-23  1:10     ` Benjamin Herrenschmidt
2017-07-24 13:48     ` Michael Ellerman
2017-07-19  4:49 ` [PATCH 03/24] powerpc/6xx: Handle DABR match before calling do_page_fault Benjamin Herrenschmidt
2017-08-03  0:19   ` Michael Ellerman
2017-08-03  1:00     ` Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 04/24] powerpc/mm: Update definitions of DSISR bits Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 05/24] powerpc/mm: Update bits used to skip hash_page Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 06/24] powerpc/mm: Use symbolic constants for filtering SRR1 bits on ISIs Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 07/24] powerpc/mm: Move out definition of CPU specific is_write bits Benjamin Herrenschmidt
2017-07-22 16:40   ` LEROY Christophe
2017-07-23  1:06     ` Benjamin Herrenschmidt
2017-07-24 11:58     ` Michael Ellerman
2017-07-19  4:49 ` [PATCH 08/24] powerpc/mm: Move error_code checks for bad faults earlier Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 09/24] powerpc/mm: Overhaul handling of bad page faults Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 10/24] powerpc/mm: Move debugger check to notify_page_fault() Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 11/24] powerpc/mm: Simplify returns from __do_page_fault Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 12/24] powerpc/mm: Fix reporting of kernel execute faults Benjamin Herrenschmidt
2018-11-07  8:35   ` Christophe LEROY
2018-11-07 10:39     ` Benjamin Herrenschmidt
     [not found]     ` <87zhtr5d1v.fsf@linux.ibm.com>
2018-11-30  6:08       ` Christophe LEROY
2017-07-19  4:49 ` [PATCH 13/24] powerpc/mm: Make bad_area* helper functions Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 14/24] powerpc/mm: Rework mm_fault_error() Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 15/24] powerpc/mm: Move CMO accounting out of do_page_fault into a helper Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 16/24] powerpc/mm: Cosmetic fix to page fault accounting Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 17/24] powerpc/mm: Move the DSISR_PROTFAULT sanity check Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 18/24] powerpc/mm: Move/simplify faulthandler_disabled() and !mm check Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 19/24] powerpc/mm: Add a bunch of (un)likely annotations to do_page_fault Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 20/24] powerpc/mm: Set fault flags earlier Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 21/24] powerpc/mm: Move page fault VMA access checks to a helper Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 22/24] powerpc/mm: Don't lose "major" fault indication on retry Benjamin Herrenschmidt
2017-07-19  4:49 ` [PATCH 23/24] powerpc/mm: Cleanup check for stack expansion Benjamin Herrenschmidt
2017-07-21 16:59   ` LEROY Christophe
2017-07-24 10:47     ` Michael Ellerman
2017-07-24 17:34       ` LEROY Christophe
2017-07-25 11:19         ` Michael Ellerman [this message]
2017-07-31 11:37           ` Christophe LEROY
2017-07-19  4:49 ` [PATCH 24/24] powerpc: Remove old unused icswx based coprocessor support Benjamin Herrenschmidt
2017-08-07 10:41 ` [01/24] powerpc/mm: Move exception_enter/exit to a do_page_fault wrapper Michael Ellerman
2017-08-07 16:37   ` Christophe LEROY
2017-08-08  2:16     ` Michael Ellerman
2017-08-08  6:45       ` Christophe LEROY
2017-08-08 10:00         ` Michael Ellerman

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