From patchwork Mon Mar 14 11:54:03 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 551293 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E4EF4C4167D for ; Mon, 14 Mar 2022 12:12:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241030AbiCNMMx (ORCPT ); Mon, 14 Mar 2022 08:12:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242385AbiCNMJz (ORCPT ); Mon, 14 Mar 2022 08:09:55 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDD1A39F; Mon, 14 Mar 2022 05:07:46 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 95BCEB80CDE; Mon, 14 Mar 2022 12:07:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FDA2C340E9; Mon, 14 Mar 2022 12:07:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1647259664; bh=Y9KlIpkBRHEF52Fy9TTBs0ebsuplB+fl+zs/LguYyZs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fBBH+dOYRTDM9SX2ZZMvjDZ2aT31Ld1rz324LH/usCNnLmFXgJrZO1qhQYIPpvrCr AxOM7bY0X9rchjGL88pFk9tibh4Vdri1BvvWE3NrNr1DPL0LlxPukPuWmjg1uJXnh/ i0dp4jIj99mL7vD6iUc3mBHs9ahqnhkbPyr5bpaI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Wanpeng Li , Paolo Bonzini , Sasha Levin Subject: [PATCH 5.15 061/110] x86/kvm: Dont use pv tlb/ipi/sched_yield if on 1 vCPU Date: Mon, 14 Mar 2022 12:54:03 +0100 Message-Id: <20220314112744.738007397@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220314112743.029192918@linuxfoundation.org> References: <20220314112743.029192918@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Wanpeng Li [ Upstream commit ec756e40e271866f951d77c5e923d8deb6002b15 ] Inspired by commit 3553ae5690a (x86/kvm: Don't use pvqspinlock code if only 1 vCPU), on a VM with only 1 vCPU, there is no need to enable pv tlb/ipi/sched_yield and we can save the memory for __pv_cpu_mask. Signed-off-by: Wanpeng Li Message-Id: <1645171838-2855-1-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- arch/x86/kernel/kvm.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index b656456c3a94..811c7aaf23aa 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -457,19 +457,22 @@ static bool pv_tlb_flush_supported(void) { return (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) && !kvm_para_has_hint(KVM_HINTS_REALTIME) && - kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)); + kvm_para_has_feature(KVM_FEATURE_STEAL_TIME) && + (num_possible_cpus() != 1)); } static bool pv_ipi_supported(void) { - return kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI); + return (kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI) && + (num_possible_cpus() != 1)); } static bool pv_sched_yield_supported(void) { return (kvm_para_has_feature(KVM_FEATURE_PV_SCHED_YIELD) && !kvm_para_has_hint(KVM_HINTS_REALTIME) && - kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)); + kvm_para_has_feature(KVM_FEATURE_STEAL_TIME) && + (num_possible_cpus() != 1)); } #define KVM_IPI_CLUSTER_SIZE (2 * BITS_PER_LONG)