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 26647C433F5 for ; Tue, 1 Mar 2022 20:15:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237782AbiCAUPk (ORCPT ); Tue, 1 Mar 2022 15:15:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237706AbiCAUPc (ORCPT ); Tue, 1 Mar 2022 15:15:32 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B69E75624; Tue, 1 Mar 2022 12:14:48 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 0AE446170C; Tue, 1 Mar 2022 20:14:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0CE0EC340EE; Tue, 1 Mar 2022 20:14:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646165687; bh=TUKvDE7Yn53C+D24wIJTRkOEGDhyfiTrS45tDJ3cE4k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BYhIAU4bIMG9G26zapqFpMmhl+LyHqPoC1RTqJaCS8PGjFLoLvEA8AGXc9II6v9DP qek59k5T/2l+5SeAqcOKgwSMOtjO+pZZu0FIod0zWvJmPegKrjaSzWS8bINjvuatAP ZKLp3c29V3hgf8C5G3J+vTNbiEYWy8TQ+/hdubXCM5hdXecnFLhD8xHuhjP6Rj64um O+a1RjpPTlnggVDZuV9QZ5Jdew0EW4tNDFBd0Pdu/INfwh1Fav9EKIQakKkjYuKFwK bxszO2OBhSu1wvcG1qyHNyWXklfO+SIfeOqxJxg6Htez8noODqA919FW6VuM7KHhc7 9wWZkqn0bq6KA== 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 5.16 12/28] x86/kvm: Don't use pv tlb/ipi/sched_yield if on 1 vCPU Date: Tue, 1 Mar 2022 15:13:17 -0500 Message-Id: <20220301201344.18191-12-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220301201344.18191-1-sashal@kernel.org> References: <20220301201344.18191-1-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: 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 59abbdad7729c..ff3db164e52cb 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -462,19 +462,22 @@ 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