From patchwork Mon Sep 9 13:48:03 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 11137987 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 26FD914E5 for ; Mon, 9 Sep 2019 13:49:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0211120828 for ; Mon, 9 Sep 2019 13:49:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568036966; bh=DyqUvs5n5vZlYBUiIS+yVwEOdZUEafyi7zk2O3h9puo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ORGBNEGrF5GxsJVW8OH41fP2wQN+2k+/hhT7fGYkfgetU6Yka1jO7edLimLXca9VP Sh5sA6y+DHey7Uo6luqme0ncNPScXyidsj9ZXRwsLKlbFYuSndlYYcxOQw4eMSgTZZ 6H2+HsPRW79zMDMpWcrid0bY1RT9SddmCTWJLE7I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404926AbfIINtZ (ORCPT ); Mon, 9 Sep 2019 09:49:25 -0400 Received: from foss.arm.com ([217.140.110.172]:50742 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404913AbfIINtY (ORCPT ); Mon, 9 Sep 2019 09:49:24 -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 30E621B8E; Mon, 9 Sep 2019 06:49:24 -0700 (PDT) Received: from localhost.localdomain (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 126283F59C; Mon, 9 Sep 2019 06:49:21 -0700 (PDT) From: Marc Zyngier To: Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= Cc: Alexandru Elisei , Andre Przywara , Eric Auger , James Morse , Mark Rutland , Zenghui Yu , kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: [PATCH 13/17] KVM: Call kvm_arch_vcpu_blocking early into the blocking sequence Date: Mon, 9 Sep 2019 14:48:03 +0100 Message-Id: <20190909134807.27978-14-maz@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190909134807.27978-1-maz@kernel.org> References: <20190909134807.27978-1-maz@kernel.org> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org When a vpcu is about to block by calling kvm_vcpu_block, we call back into the arch code to allow any form of synchronization that may be required at this point (SVN stops the AVIC, ARM synchronises the VMCR and enables GICv4 doorbells). But this synchronization comes in quite late, as we've potentially waited for halt_poll_ns to expire. Instead, let's move kvm_arch_vcpu_blocking() to the beginning of kvm_vcpu_block(), which on ARM has several benefits: - VMCR gets synchronised early, meaning that any interrupt delivered during the polling window will be evaluated with the correct guest PMR - GICv4 doorbells are enabled, which means that any guest interrupt directly injected during that window will be immediately recognised Tang Nianyao ran some tests on a GICv4 machine to evaluate such change, and reported up to a 10% improvement for netperf: netperf result: D06 as server, intel 8180 server as client with change: package 512 bytes - 5500 Mbits/s package 64 bytes - 760 Mbits/s without change: package 512 bytes - 5000 Mbits/s package 64 bytes - 710 Mbits/s Acked-by: Paolo Bonzini Signed-off-by: Marc Zyngier --- virt/kvm/kvm_main.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index c6a91b044d8d..e6de3159e682 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2321,6 +2321,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) bool waited = false; u64 block_ns; + kvm_arch_vcpu_blocking(vcpu); + start = cur = ktime_get(); if (vcpu->halt_poll_ns && !kvm_arch_no_poll(vcpu)) { ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns); @@ -2341,8 +2343,6 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) } while (single_task_running() && ktime_before(cur, stop)); } - kvm_arch_vcpu_blocking(vcpu); - for (;;) { prepare_to_swait_exclusive(&vcpu->wq, &wait, TASK_INTERRUPTIBLE); @@ -2355,9 +2355,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) finish_swait(&vcpu->wq, &wait); cur = ktime_get(); - - kvm_arch_vcpu_unblocking(vcpu); out: + kvm_arch_vcpu_unblocking(vcpu); block_ns = ktime_to_ns(cur) - ktime_to_ns(start); if (!vcpu_valid_wakeup(vcpu))