From patchwork Thu Nov 7 16:04:10 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 11233271 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 635861390 for ; Thu, 7 Nov 2019 16:04:33 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2E085218AE for ; Thu, 7 Nov 2019 16:04:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Blwo1XPp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E085218AE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:To :From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=PoAnrEwSAtFpuZIKAdQhcZYyVShC+Hc3xepaIGuUs0o=; b=Blwo1XPpE2JiWN LnlgcBZyELx3Skze9OB+ff84z4PJUR+zV0aOedUKDUSx9XIQFnCYz5mYK4mIcj8OJvVjXwsLDmMBp q+Cd2mnmVikmi8mIZsP4dB0S7yjdoFPqabYnhZYDKGt1VJZC7SfzM8NcD6JvXrYpF5nwCZeypXO32 5a7xPgNB8VrtJf9yXKAKfFq3danCwoVNbGokmO5bhihXU8p0RWvfEO3uN1d+1f39DU9pMtVW/SEph MmfW/TulWoeUT2rj3t7/lZF3+4TvLaTR0FMzJMCKIN70fyse/1TVBGLIWfgTBuwbrsfF3us2ck9oY VcvUOb8J9i+ouUkm74iw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iSkGr-0005jr-I9; Thu, 07 Nov 2019 16:04:29 +0000 Received: from inca-roads.misterjones.org ([213.251.177.50]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iSkGo-0005iC-BJ for linux-arm-kernel@lists.infradead.org; Thu, 07 Nov 2019 16:04:27 +0000 Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.lan) by cheepnis.misterjones.org with esmtpsa (TLSv1.2:DHE-RSA-AES128-GCM-SHA256:128) (Exim 4.80) (envelope-from ) id 1iSkGk-0008Bm-6O; Thu, 07 Nov 2019 17:04:22 +0100 From: Marc Zyngier To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: [PATCH 0/2] KVM: arm64: Reduce occurence of GICv4 doorbells on non-oversubscribed systems Date: Thu, 7 Nov 2019 16:04:10 +0000 Message-Id: <20191107160412.30301-1-maz@kernel.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on cheepnis.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191107_080426_537984_4B937219 X-CRM114-Status: GOOD ( 11.59 ) X-Spam-Score: 1.0 (+) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (1.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record 1.0 SPF_SOFTFAIL SPF: sender does not match SPF record (softfail) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: James Morse , Julien Thierry , Suzuki K Poulose Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org As I was cleaning up some of the GICv4 code to make way for GICv4.1 it occured to me that we could drastically reduce the impact of the GICv4 doorbells on systems that are not oversubscribed (each vcpu "owns" a physical CPU). The technique borrows its logic from the way we disable WFE trapping when a vcpu is the only process on the CPU run-queue. If this vcpu is the target of VLPIs, it is then beneficial not to trap blocking WFIs and to leave the vcpu waiting for interrupts in guest state. All we need to do here is to track whether VLPIs are associated to a vcpu (which is easily done by using a counter that we update on MAPI, DISCARD and MOVI). It has been *very lightly* tested on a D05, and behaved pretty well in my limited test cases (I get almost no doorbell at all in the non oversubscribed case, and the usual hailstorm as soon as there is oversubscription). I'd welcome some testing on more current HW. Marc Zyngier (2): KVM: vgic-v4: Track the number of VLPIs per vcpu KVM: arm64: Opportunistically turn off WFI trapping when using direct LPI injection arch/arm/include/asm/kvm_emulate.h | 4 ++-- arch/arm64/include/asm/kvm_emulate.h | 9 +++++++-- include/linux/irqchip/arm-gic-v4.h | 2 ++ virt/kvm/arm/arm.c | 4 ++-- virt/kvm/arm/vgic/vgic-init.c | 1 + virt/kvm/arm/vgic/vgic-its.c | 3 +++ virt/kvm/arm/vgic/vgic-v4.c | 2 ++ 7 files changed, 19 insertions(+), 6 deletions(-) Reviewed-by: Christoffer Dall