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From: Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v6 03/24] mm: Dont assume page-table invariance during faults
References: <1515777968-867-1-git-send-email-ldufour@linux.vnet.ibm.com>
	<1515777968-867-4-git-send-email-ldufour@linux.vnet.ibm.com>
Date: Tue, 16 Jan 2018 19:04:12 -0800
In-Reply-To: <1515777968-867-4-git-send-email-ldufour@linux.vnet.ibm.com>
	(Laurent Dufour's message of "Fri, 12 Jan 2018 18:25:47 +0100")
Message-ID: <87d129tccz.fsf@linux.intel.com>
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To: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: paulmck@linux.vnet.ibm.com, peterz@infradead.org, akpm@linux-foundation.org, kirill@shutemov.name, mhocko@kernel.org, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox <willy@infradead.org>, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, hpa@zytor.com, Will Deacon <will.deacon@arm.com>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Andrea Arcangeli <aarcange@redhat.com>, Alexei Starovoitov <alexei.starovoitov@gmail.com>, kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, Tim Chen <tim.c.chen@linux.intel.com>, linuxppc-dev@lists.ozlabs.org, x86@kernel.org

Laurent Dufour <ldufour@linux.vnet.ibm.com> writes:

> From: Peter Zijlstra <peterz@infradead.org>
>
> One of the side effects of speculating on faults (without holding
> mmap_sem) is that we can race with free_pgtables() and therefore we
> cannot assume the page-tables will stick around.
>
> Remove the reliance on the pte pointer.

This needs a lot more explanation. So why is this code not needed with
SPF only?

-Andi

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