From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F85CC433FE for ; Sun, 10 Oct 2021 15:09:33 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 9DCDF61058 for ; Sun, 10 Oct 2021 15:09:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9DCDF61058 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 4EC624B0BF; Sun, 10 Oct 2021 11:09:32 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ipNiR7fJWcBo; Sun, 10 Oct 2021 11:09:31 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 3518A4B125; Sun, 10 Oct 2021 11:09:29 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 29B984B0A0 for ; Sun, 10 Oct 2021 11:09:27 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8N0jxvG1jBP1 for ; Sun, 10 Oct 2021 11:09:26 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 0E7DD4B0B6 for ; Sun, 10 Oct 2021 11:09:26 -0400 (EDT) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3E4616109E; Sun, 10 Oct 2021 15:09:25 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mZaS3-00FrmD-EK; Sun, 10 Oct 2021 16:09:23 +0100 From: Marc Zyngier To: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 3/5] KVM: arm64: vgic-v3: Reduce common group trapping to ICV_DIR_EL1 when possible Date: Sun, 10 Oct 2021 16:09:08 +0100 Message-Id: <20211010150910.2911495-4-maz@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211010150910.2911495-1-maz@kernel.org> References: <20211010150910.2911495-1-maz@kernel.org> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, james.morse@arm.com, suzuki.poulose@arm.com, alexandru.elisei@arm.com, eric.auger@redhat.com, joey.gouly@arm.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: kernel-team@android.com, Joey Gouly X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On systems that advertise ICH_VTR_EL2.SEIS, we trap all GICv3 sysreg accesses from the guest. From a performance perspective, this is OK as long as the guest doesn't hammer the GICv3 CPU interface. In most cases, this is fine, unless the guest actively uses priorities and switches PMR_EL1 very often. Which is exactly what happens when a Linux guest runs with irqchip.gicv3_pseudo_nmi=1. In these condition, the performance plumets as we hit PMR each time we mask/unmask interrupts. Not good. There is however an opportunity for improvement. Careful reading of the architecture specification indicates that the only GICv3 sysreg belonging to the common group (which contains the SGI registers, PMR, DIR, CTLR and RPR) that is allowed to generate a SError is DIR. Everything else is safe. It is thus possible to substitute the trapping of all the common group with just that of DIR if it supported by the implementation. Yes, that's yet another optional bit of the architecture. So let's just do that, as it leads to some impressive result on the M1: Without this change: bash-5.1# /host/home/maz/hackbench 100 process 1000 Running with 100*40 (== 4000) tasks. Time: 56.596 With this change: bash-5.1# /host/home/maz/hackbench 100 process 1000 Running with 100*40 (== 4000) tasks. Time: 8.649 which is a pretty convincing result. Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/sysreg.h | 3 +++ arch/arm64/kvm/vgic/vgic-v3.c | 15 +++++++++++---- 2 files changed, 14 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index b268082d67ed..9412a645a1c0 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -1152,6 +1152,7 @@ #define ICH_HCR_TC (1 << 10) #define ICH_HCR_TALL0 (1 << 11) #define ICH_HCR_TALL1 (1 << 12) +#define ICH_HCR_TDIR (1 << 14) #define ICH_HCR_EOIcount_SHIFT 27 #define ICH_HCR_EOIcount_MASK (0x1f << ICH_HCR_EOIcount_SHIFT) @@ -1184,6 +1185,8 @@ #define ICH_VTR_SEIS_MASK (1 << ICH_VTR_SEIS_SHIFT) #define ICH_VTR_A3V_SHIFT 21 #define ICH_VTR_A3V_MASK (1 << ICH_VTR_A3V_SHIFT) +#define ICH_VTR_TDS_SHIFT 19 +#define ICH_VTR_TDS_MASK (1 << ICH_VTR_TDS_SHIFT) #define ARM64_FEATURE_FIELD_BITS 4 diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c index ae59e2580bf5..467c22bbade6 100644 --- a/arch/arm64/kvm/vgic/vgic-v3.c +++ b/arch/arm64/kvm/vgic/vgic-v3.c @@ -15,6 +15,7 @@ static bool group0_trap; static bool group1_trap; static bool common_trap; +static bool dir_trap; static bool gicv4_enable; void vgic_v3_set_underflow(struct kvm_vcpu *vcpu) @@ -296,6 +297,8 @@ void vgic_v3_enable(struct kvm_vcpu *vcpu) vgic_v3->vgic_hcr |= ICH_HCR_TALL1; if (common_trap) vgic_v3->vgic_hcr |= ICH_HCR_TC; + if (dir_trap) + vgic_v3->vgic_hcr |= ICH_HCR_TDIR; } int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq) @@ -676,14 +679,18 @@ int vgic_v3_probe(const struct gic_kvm_info *info) group0_trap = true; group1_trap = true; - common_trap = true; + if (ich_vtr_el2 & ICH_VTR_TDS_MASK) + dir_trap = true; + else + common_trap = true; } - if (group0_trap || group1_trap || common_trap) { - kvm_info("GICv3 sysreg trapping enabled ([%s%s%s], reduced performance)\n", + if (group0_trap || group1_trap || common_trap | dir_trap) { + kvm_info("GICv3 sysreg trapping enabled ([%s%s%s%s], reduced performance)\n", group0_trap ? "G0" : "", group1_trap ? "G1" : "", - common_trap ? "C" : ""); + common_trap ? "C" : "", + dir_trap ? "D" : ""); static_branch_enable(&vgic_v3_cpuif_trap); } -- 2.30.2 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm