From: Andy Lutomirski <luto@amacapital.net>
To: Andi Kleen <andi@firstfloor.org>
Cc: Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Denys Vlasenko <dvlasenk@redhat.com>,
Brian Gerst <brgerst@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Waiman Long <Waiman.Long@hp.com>
Subject: Re: why do we need vmalloc_sync_all?
Date: Sun, 14 Jun 2015 19:57:46 -0700 [thread overview]
Message-ID: <CALCETrUp5Xm1ZmzoSEGrq1D05myAUhCzNgXvv-Cga8xjEi-CeQ@mail.gmail.com> (raw)
In-Reply-To: <87bnghit74.fsf@tassilo.jf.intel.com>
On Sun, Jun 14, 2015 at 7:47 PM, Andi Kleen <andi@firstfloor.org> wrote:
> Oleg Nesterov <oleg@redhat.com> writes:
>>
>> But again, the kernel no longer does this? do_page_fault() does vmalloc_fault()
>> without notify_die(). If it fails, I do not see how/why a modular DIE_OOPS
>> handler could try to resolve this problem and trigger another fault.
>
> The same problem can happen from NMI handlers or machine check
> handlers. It's not necessarily tied to page faults only.
AIUI, the point of the one and only vmalloc_sync_all call is to
prevent infinitely recursive faults when we call a notify_die
callback. The only thing that it could realistically protect is
module text or static non-per-cpu module data, since that's the only
thing that's reliably already in the init pgd. I'm with Oleg: I don't
see how that can happen, since do_page_fault fixes up vmalloc faults
before it calls notify_die.
--Andy
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next prev parent reply other threads:[~2015-06-15 2:58 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-13 9:49 [PATCH 00/12, v2] x86/mm: Implement lockless pgd_alloc()/pgd_free() Ingo Molnar
2015-06-13 9:49 ` [PATCH 01/12] x86/mm/pat: Don't free PGD entries on memory unmap Ingo Molnar
2015-06-13 9:49 ` [PATCH 02/12] x86/mm/hotplug: Remove pgd_list use from the memory hotplug code Ingo Molnar
2015-06-13 19:24 ` Oleg Nesterov
2015-06-14 7:36 ` Ingo Molnar
2015-06-14 19:24 ` Oleg Nesterov
2015-06-14 19:38 ` Oleg Nesterov
2015-06-15 0:40 ` Paul E. McKenney
2015-06-15 20:33 ` Ingo Molnar
2015-06-13 9:49 ` [PATCH 03/12] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Ingo Molnar
2015-06-13 9:49 ` [PATCH 04/12] x86/mm/hotplug: Simplify sync_global_pgds() Ingo Molnar
2015-06-13 9:49 ` [PATCH 05/12] mm: Introduce arch_pgd_init_late() Ingo Molnar
2015-06-13 9:49 ` [PATCH 06/12] x86/mm: Enable and use the arch_pgd_init_late() method Ingo Molnar
2015-06-13 9:49 ` [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code Ingo Molnar
2015-06-14 8:26 ` Ingo Molnar
2015-06-15 9:05 ` Ian Campbell
2015-06-15 10:30 ` David Vrabel
2015-06-15 20:35 ` Ingo Molnar
2015-06-16 14:15 ` David Vrabel
2015-06-16 14:19 ` Boris Ostrovsky
2015-06-16 14:27 ` David Vrabel
2015-06-13 9:49 ` [PATCH 08/12] x86/mm: Remove pgd_list use from vmalloc_sync_all() Ingo Molnar
2015-06-13 9:49 ` [PATCH 09/12] x86/mm/pat/32: Remove pgd_list use from the PAT code Ingo Molnar
2015-06-13 9:49 ` [PATCH 10/12] x86/mm: Make pgd_alloc()/pgd_free() lockless Ingo Molnar
2015-06-13 9:49 ` [PATCH 11/12] x86/mm: Remove pgd_list leftovers Ingo Molnar
2015-06-13 9:49 ` [PATCH 12/12] x86/mm: Simplify pgd_alloc() Ingo Molnar
2015-06-13 18:58 ` why do we need vmalloc_sync_all? Oleg Nesterov
2015-06-14 7:59 ` Ingo Molnar
2015-06-14 20:06 ` Oleg Nesterov
2015-06-15 2:47 ` Andi Kleen
2015-06-15 2:57 ` Andy Lutomirski [this message]
2015-06-15 20:28 ` Ingo Molnar
2015-06-15 20:48 ` Andy Lutomirski
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