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From: Dave Hansen <dave.hansen@intel.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
	LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	Linux-MM <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: Use higher-order pages in vmalloc
Date: Thu, 22 Feb 2018 11:36:13 -0800	[thread overview]
Message-ID: <cf07fba1-a787-9af3-682f-309ac52c9345@intel.com> (raw)
In-Reply-To: <CALCETrUeSgVmjgNsUg+0sAacq_VeHsEPqOkRfHkij4xmADM_5A@mail.gmail.com>

On 02/22/2018 11:27 AM, Andy Lutomirski wrote:
> On Thu, Feb 22, 2018 at 7:19 PM, Dave Hansen <dave.hansen@intel.com> wrote:
>> On 02/22/2018 11:01 AM, Andy Lutomirski wrote:
>>> On x86, if you shoot down the PTE for the current stack, you're dead.
>>
>> *If* we were to go do this insanity for vmalloc()'d memory, we could
>> probably limit it to kswapd, and also make sure that kernel threads
>> don't get vmalloc()'d stacks or that we mark them in a way to say we
>> never muck with them.
> 
> How does that help?  We need to make sure that the task whose stack
> we're migrating is (a) not running and (b) is not being switched in or
> out.  And we have to make sure that there isn't some *other* mm that
> has the task's stack in ASID's TLB space.
> 
> Maybe we take some lock so the task can't run, then flush the world,
> then release the lock.

Oh, I was thinking only of the case where you try to muck with your
*own* stack.  But, I see what you are saying about doing it to another
task on another CPU that is actively using the stack.

I think what you're saying is that we do not want to handle faults that
are caused by %esp being unusable.  Whatever we do, we've got to make
sure that no CPU has a stack in %esp that we are messing with.

  reply	other threads:[~2018-02-22 19:36 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-23 10:55 [PATCH 1/4] vmalloc: add vm_flags argument to internal __vmalloc_node() Konstantin Khlebnikov
2018-01-23 10:55 ` [PATCH 2/4] vmalloc: add __vmalloc_area() Konstantin Khlebnikov
2018-01-23 10:55 ` [PATCH 3/4] kernel/fork: switch vmapped stack callation to __vmalloc_area() Konstantin Khlebnikov
2018-01-23 13:57   ` Konstantin Khlebnikov
2018-02-21  0:16     ` Andrew Morton
2018-02-21  7:23       ` Konstantin Khlebnikov
2018-02-21 16:35         ` Andy Lutomirski
2018-01-23 10:55 ` [PATCH 4/4] kernel/fork: add option to use virtually mapped stacks as fallback Konstantin Khlebnikov
2018-02-21 15:42   ` Use higher-order pages in vmalloc Matthew Wilcox
2018-02-21 16:11     ` Andy Lutomirski
2018-02-21 16:50       ` Matthew Wilcox
2018-02-21 16:16     ` Dave Hansen
2018-02-21 17:01       ` Matthew Wilcox
2018-02-22  6:59         ` Michal Hocko
2018-02-22 12:22           ` Matthew Wilcox
2018-02-22 13:36             ` Michal Hocko
2018-02-22 19:01               ` Andy Lutomirski
2018-02-22 19:19                 ` Dave Hansen
2018-02-22 19:27                   ` Andy Lutomirski
2018-02-22 19:36                     ` Dave Hansen [this message]
2018-02-23 12:13                 ` Michal Hocko
2018-03-01 18:16                   ` Eric Dumazet
2018-02-21 12:24 ` [PATCH 1/4] vmalloc: add vm_flags argument to internal __vmalloc_node() Matthew Wilcox
2018-02-21 12:39   ` Andrey Ryabinin

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