From mboxrd@z Thu Jan 1 00:00:00 1970 From: Izik Eidus Subject: set_pte_at_notify regression Date: Fri, 10 Jan 2014 18:38:06 +0200 Message-ID: <52D021EE.3020104@ravellosystems.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: linux-mm@kvack.org, kvm@vger.kernel.org, aarcange@redhat.com, Alex Fishman , Mike Rapoport Return-path: Sender: owner-linux-mm@kvack.org List-Id: kvm.vger.kernel.org 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org