From patchwork Tue Jun 11 17:03:27 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 10987857 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 8A32414DB for ; Tue, 11 Jun 2019 17:03:57 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 73B982807B for ; Tue, 11 Jun 2019 17:03:57 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 68017285D4; Tue, 11 Jun 2019 17:03:57 +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=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 0B301285A8 for ; Tue, 11 Jun 2019 17:03:57 +0000 (UTC) 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=vFTFzavLLtvd1q+KxvOOhkYlll4CU2EbiRUkHp48Pas=; b=mTHuKAqhOpzgrk KvabdR3eLBo80qaKZxsrS5/v3CE6ZHC4P7YQgWUpzkoa4Qfu/wmpTliv1ldeGTUIDFBvmNt/ZuEXa hIukQCr72ptD3UHVLac0kABocLMIT445bPdsyAIcgWLqbWCdDfPtn3jJd4XVxMKGUQwtSRPNyYucg K4H3b11/rDMnlKOiygFgx9SbvSOFxWAibGsKvlM2cjB2ncBg0Sz9aWJBtbKf1cAzmLzu5mT4Gr8ow rCi2jwZq9tGd5BTvMv7F+7Dc0yzsRIZiDzEPwdsnXZp9hSWWSOHx2xyHCoXFjnCZ8eGx3CVUIrZyV q2YdQwZXDJ+jjb6ZduJQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hakBc-0000Vo-8U; Tue, 11 Jun 2019 17:03:52 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hakBY-0000VE-PD for linux-arm-kernel@lists.infradead.org; Tue, 11 Jun 2019 17:03:50 +0000 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 BD777337; Tue, 11 Jun 2019 10:03:47 -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 4D7AB3F73C; Tue, 11 Jun 2019 10:03:46 -0700 (PDT) From: Marc Zyngier To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org Subject: [PATCH v2 0/9] KVM: arm/arm64: vgic: ITS translation cache Date: Tue, 11 Jun 2019 18:03:27 +0100 Message-Id: <20190611170336.121706-1-marc.zyngier@arm.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190611_100348_909060_31DCE302 X-CRM114-Status: GOOD ( 13.84 ) 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: Suzuki K Poulose , "Raslan, KarimAllah" , Julien Thierry , Christoffer Dall , Eric Auger , James Morse , Zenghui Yu , "Saidi, Ali" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP It recently became apparent[1] that our LPI injection path is not as efficient as it could be when injecting interrupts coming from a VFIO assigned device. Although the proposed patch wasn't 100% correct, it outlined at least two issues: (1) Injecting an LPI from VFIO always results in a context switch to a worker thread: no good (2) We have no way of amortising the cost of translating a DID+EID pair to an LPI number The reason for (1) is that we may sleep when translating an LPI, so we do need a context process. A way to fix that is to implement a small LPI translation cache that could be looked up from an atomic context. It would also solve (2). This is what this small series proposes. It implements a very basic LRU cache of pre-translated LPIs, which gets used to implement kvm_arch_set_irq_inatomic. The size of the cache is currently hard-coded at 16 times the number of vcpus, a number I have picked under the influence of Ali Saidi. If that's not enough for you, blame me, though. Does it work? well, it doesn't crash, and is thus perfect. More seriously, I don't really have a way to benchmark it directly, so my observations are only indirect: On a TX2 system, I run a 4 vcpu VM with an Ethernet interface passed to it directly. From the host, I inject interrupts using debugfs. In parallel, I look at the number of context switch, and the number of interrupts on the host. Without this series, I get the same number for both IRQ and CS (about half a million of each per second is pretty easy to reach). With this series, the number of context switches drops to something pretty small (in the low 2k), while the number of interrupts stays the same. Yes, this is a pretty rubbish benchmark, what did you expect? ;-) So I'm putting this out for people with real workloads to try out and report what they see. [1] https://lore.kernel.org/lkml/1552833373-19828-1-git-send-email-yuzenghui@huawei.com/ * From v1: - Fixed race on allocation, where the same LPI could be cached multiple times - Now invalidate the cache on vgic teardown, avoiding memory leaks - Change patch split slightly, general reshuffling - Small cleanups here and there - Rebased on 5.2-rc4 Marc Zyngier (9): KVM: arm/arm64: vgic: Add LPI translation cache definition KVM: arm/arm64: vgic: Add __vgic_put_lpi_locked primitive KVM: arm/arm64: vgic-its: Add MSI-LPI translation cache invalidation KVM: arm/arm64: vgic-its: Invalidate MSI-LPI translation cache on specific commands KVM: arm/arm64: vgic-its: Invalidate MSI-LPI translation cache on disabling LPIs KVM: arm/arm64: vgic-its: Invalidate MSI-LPI translation cache on vgic teardown KVM: arm/arm64: vgic-its: Cache successful MSI->LPI translation KVM: arm/arm64: vgic-its: Check the LPI translation cache on MSI injection KVM: arm/arm64: vgic-irqfd: Implement kvm_arch_set_irq_inatomic include/kvm/arm_vgic.h | 3 + virt/kvm/arm/vgic/vgic-init.c | 5 + virt/kvm/arm/vgic/vgic-irqfd.c | 36 +++++- virt/kvm/arm/vgic/vgic-its.c | 204 +++++++++++++++++++++++++++++++ virt/kvm/arm/vgic/vgic-mmio-v3.c | 4 +- virt/kvm/arm/vgic/vgic.c | 26 ++-- virt/kvm/arm/vgic/vgic.h | 5 + 7 files changed, 267 insertions(+), 16 deletions(-)