From patchwork Mon Aug 13 14:57:55 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 10564403 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 55E3114E2 for ; Mon, 13 Aug 2018 15:00:50 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4631129493 for ; Mon, 13 Aug 2018 15:00:50 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4460E2949B; Mon, 13 Aug 2018 15:00:50 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E0A5A29493 for ; Mon, 13 Aug 2018 15:00:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730025AbeHMRnZ (ORCPT ); Mon, 13 Aug 2018 13:43:25 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:60730 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729794AbeHMRnZ (ORCPT ); Mon, 13 Aug 2018 13:43:25 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 41DE880D; Mon, 13 Aug 2018 08:00:48 -0700 (PDT) Received: from approximate.Emea.Arm.com (approximate.Emea.Arm.com [10.4.13.119]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4FF8D3F5D0; Mon, 13 Aug 2018 08:00:45 -0700 (PDT) From: Marc Zyngier To: Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Andre Przywara , Andrew Jones , Catalin Marinas , Christoffer Dall , Dongjiu Geng , Eric Auger , "Gustavo A . R . Silva" , James Morse , Jia He , Kees Cook , Mark Rutland , Punit Agrawal , Suzuki Poulose Subject: [PATCH 37/37] KVM: arm/arm64: Skip updating PTE entry if no change Date: Mon, 13 Aug 2018 15:57:55 +0100 Message-Id: <20180813145755.16566-38-marc.zyngier@arm.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180813145755.16566-1-marc.zyngier@arm.com> References: <20180813145755.16566-1-marc.zyngier@arm.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Punit Agrawal When there is contention on faulting in a particular page table entry at stage 2, the break-before-make requirement of the architecture can lead to additional refaulting due to TLB invalidation. Avoid this by skipping a page table update if the new value of the PTE matches the previous value. Cc: stable@vger.kernel.org Fixes: d5d8184d35c9 ("KVM: ARM: Memory virtualization setup") Reviewed-by: Suzuki Poulose Acked-by: Christoffer Dall Signed-off-by: Punit Agrawal Signed-off-by: Marc Zyngier --- virt/kvm/arm/mmu.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c index 13dfe36501aa..91aaf73b00df 100644 --- a/virt/kvm/arm/mmu.c +++ b/virt/kvm/arm/mmu.c @@ -1147,6 +1147,10 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache, /* Create 2nd stage page table mapping - Level 3 */ old_pte = *pte; if (pte_present(old_pte)) { + /* Skip page table update if there is no change */ + if (pte_val(old_pte) == pte_val(*new_pte)) + return 0; + kvm_set_pte(pte, __pte(0)); kvm_tlb_flush_vmid_ipa(kvm, addr); } else {