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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5924CC43217 for ; Tue, 1 Mar 2022 20:18:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237878AbiCAUSm (ORCPT ); Tue, 1 Mar 2022 15:18:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50830 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238238AbiCAUSM (ORCPT ); Tue, 1 Mar 2022 15:18:12 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2F7EC5FFA; Tue, 1 Mar 2022 12:17:21 -0800 (PST) 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 sin.source.kernel.org (Postfix) with ESMTPS id 7B1E8CE1E66; Tue, 1 Mar 2022 20:17:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5AABC36AE3; Tue, 1 Mar 2022 20:17:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646165837; bh=CUyZj62DQefLTzMMGF+hDyJGKchgnq4fyRxIIaIvKME=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cwGh1T204qLbleTSwVpI2LAxI7MkNc1BllnV5Q2WOUiZFNg2j3JiDhYJGur5XGb8k F9k7WKMGEjpqeFPmZ/mofDQRAn2qQi3l0XRMnO3vjDtCkLTxsFphBl7amNawJr3wsa eG5clj2K3RfcrhSm7RtIoUGlyHLfsAHa16LOhogs2NGwZLOROudWP7n7Qk/elYgqyr zmmBoGdGSQLPMBUuaAJUR9wuj1cSv7iDWf5nEQYBV5jwIcCAc2l5plE9ZBz5CD/Wac haGcx3xLLfHP5LYjVIovyDvx4wqUcyvGS15d3q5Ey/TPzybFCCVXLqSjduXOLtFBC+ ipD12+qno2GrA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Wanpeng Li , Paolo Bonzini , Sasha Levin , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, kvm@vger.kernel.org Subject: [PATCH AUTOSEL 5.15 10/23] x86/kvm: Don't use pv tlb/ipi/sched_yield if on 1 vCPU Date: Tue, 1 Mar 2022 15:16:09 -0500 Message-Id: <20220301201629.18547-10-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220301201629.18547-1-sashal@kernel.org> References: <20220301201629.18547-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@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 b656456c3a944..811c7aaf23aac 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) -- 2.34.1