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From: Izik Eidus <izik.eidus@ravellosystems.com>
To: linux-mm@kvack.org, kvm@vger.kernel.org, aarcange@redhat.com,
	Alex Fishman <alex.fishman@ravellosystems.com>,
	Mike Rapoport <mike.rapoport@ravellosystems.com>
Subject: set_pte_at_notify regression
Date: Fri, 10 Jan 2014 18:38:06 +0200	[thread overview]
Message-ID: <52D021EE.3020104@ravellosystems.com> (raw)

Hi,

It look like commit 6bdb913f0a70a4dfb7f066fb15e2d6f960701d00 break the 
semantic of set_pte_at_notify.
The change of calling first to mmu_notifier_invalidate_range_start, then 
to set_pte_at_notify, and then to mmu_notifier_invalidate_range_end
not only increase the amount of locks kvm have to take and release by 
factor of 3, but in addition mmu_notifier_invalidate_range_start is zapping
the pte entry from kvm, so when set_pte_at_notify get called, it doesn`t 
have any spte to set and it acctuly get called for nothing, the result is
increasing of vmexits for kvm from both do_wp_page and replace_page, and 
broken semantic of set_pte_at_notify.

Thanks.

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             reply	other threads:[~2014-01-10 16:38 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-10 16:38 Izik Eidus [this message]
2014-01-10 16:57 ` set_pte_at_notify regression Andrea Arcangeli
2014-01-12 11:56   ` Haggai Eran
2014-01-12 11:56     ` Haggai Eran
2014-01-12 17:50     ` Andrea Arcangeli
2014-01-16  7:52       ` Haggai Eran
2014-01-16  7:52         ` Haggai Eran

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