From patchwork Fri Jun 21 09:38:24 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 11009313 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 43ABF1580 for ; Fri, 21 Jun 2019 09:42:00 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 34866289A6 for ; Fri, 21 Jun 2019 09:42:00 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 28BD8289E5; Fri, 21 Jun 2019 09:42:00 +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 C18BC289A6 for ; Fri, 21 Jun 2019 09:41:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726665AbfFUJl7 (ORCPT ); Fri, 21 Jun 2019 05:41:59 -0400 Received: from foss.arm.com ([217.140.110.172]:54214 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726666AbfFUJkP (ORCPT ); Fri, 21 Jun 2019 05:40:15 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4D4701509; Fri, 21 Jun 2019 02:40:15 -0700 (PDT) Received: from filthy-habits.cambridge.arm.com (filthy-habits.cambridge.arm.com [10.1.197.61]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EE0CD3F246; Fri, 21 Jun 2019 02:40:13 -0700 (PDT) From: Marc Zyngier To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org Cc: Andre Przywara , Christoffer Dall , Dave Martin , Jintack Lim , Julien Thierry , James Morse , Suzuki K Poulose Subject: [PATCH 40/59] KVM: arm64: nv: Don't always start an S2 MMU search from the beginning Date: Fri, 21 Jun 2019 10:38:24 +0100 Message-Id: <20190621093843.220980-41-marc.zyngier@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190621093843.220980-1-marc.zyngier@arm.com> References: <20190621093843.220980-1-marc.zyngier@arm.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Starting a S2 MMU search from the beginning all the time means that we're potentially nuking a useful context (like we'd potentially have on a !VHE KVM guest). Instead, let's always start the search from the point *after* the last allocated context. This should ensure that alternating between two EL1 contexts will not result in nuking the whole S2 each time. lookup_s2_mmu now has a chance to provide a hit. Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/kvm/nested.c | 14 ++++++++++++-- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index b71a7a237f95..b7c44adcdbf3 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -123,6 +123,7 @@ struct kvm_arch { */ struct kvm_s2_mmu *nested_mmus; size_t nested_mmus_size; + int nested_mmus_next; /* VTCR_EL2 value for this VM */ u64 vtcr; diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 09afafbdc8fe..214d59019935 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -363,14 +363,24 @@ static struct kvm_s2_mmu *get_s2_mmu_nested(struct kvm_vcpu *vcpu) if (s2_mmu) goto out; - for (i = 0; i < kvm->arch.nested_mmus_size; i++) { - s2_mmu = &kvm->arch.nested_mmus[i]; + /* + * Make sure we don't always search from the same point, or we + * will always reuse a potentially active context, leaving + * free contexts unused. + */ + for (i = kvm->arch.nested_mmus_next; + i < (kvm->arch.nested_mmus_size + kvm->arch.nested_mmus_next); + i++) { + s2_mmu = &kvm->arch.nested_mmus[i % kvm->arch.nested_mmus_size]; if (atomic_read(&s2_mmu->refcnt) == 0) break; } BUG_ON(atomic_read(&s2_mmu->refcnt)); /* We have struct MMUs to spare */ + /* Set the scene for the next search */ + kvm->arch.nested_mmus_next = (i + 1) % kvm->arch.nested_mmus_size; + if (kvm_s2_mmu_valid(s2_mmu)) { /* Clear the old state */ kvm_unmap_stage2_range(s2_mmu, 0, kvm_phys_size(kvm));