linux-kernel - Re: [PATCH] kvm: Faults which trigger IO release the mmap

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Message-ID: <20140917114214.GB30733@minantech.com>
Date:	Wed, 17 Sep 2014 14:42:15 +0300
From:	Gleb Natapov <gleb@...nel.org>
To:	Radim Krčmář <rkrcmar@...hat.com>
Cc:	Andres Lagar-Cavilla <andreslc@...gle.com>,
	Gleb Natapov <gleb@...hat.com>, Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>,
	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Jianyu Zhan <nasa4836@...il.com>,
	Paul Cassella <cassella@...y.com>,
	Hugh Dickins <hughd@...gle.com>,
	Peter Feiner <pfeiner@...gle.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] kvm: Faults which trigger IO release the mmap_sem

On Wed, Sep 17, 2014 at 01:27:14PM +0200, Radim Krčmář wrote:
> 2014-09-17 13:26+0300, Gleb Natapov:
> > For async_pf_execute() you do not need to even retry. Next guest's page fault
> > will retry it for you.
> 
> Wouldn't that be a waste of vmentries?
This is how it will work with or without this second gup. Page is not
mapped into a shadow page table on this path, it happens on a next fault.

--
			Gleb.
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