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 5320AC433EF for ; Wed, 27 Apr 2022 15:55:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240623AbiD0P6Q (ORCPT ); Wed, 27 Apr 2022 11:58:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240753AbiD0P6H (ORCPT ); Wed, 27 Apr 2022 11:58:07 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8F26077F2F; Wed, 27 Apr 2022 08:54:38 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 60C6E61B4D; Wed, 27 Apr 2022 15:54:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0BD97C385AD; Wed, 27 Apr 2022 15:54:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1651074875; bh=nt4Jl+T/r56aML4HwP1tjND6t2tSipFlS5Q/81Noaz0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=G/QKHXHMD9uFlfq5qvqlsSkSfCtHLDWNpspub7lz51EJx9XkzDuBNxK8LQjgVSh6n JnyOUwnuQr/tp0RSYp5u7A1XYEOZ2sVGKdtewWHkyPWyX2El/KvGZIpdIm8r9iT6ES 00K0zFYkLkZStOdTR+zrkkLHRf3QYC4qiUO/3gPqqX8Zaplm14sVo3GE6yl9qsiGvy EC6+9Zt0EqU6146Re86vo9NDuhkQBFQ3kjT0av7QN9ZYjRwmEXWyukLnBWeNGhxLPQ GddfAdlvPOvcPjAxXotIViuTddH3fWRsUMZH/lg0r75u+QkLu2MpQQfUbRLAHqXEKa lPBDuQLIOmWLw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Wanpeng Li , Aili Yao , Sean Christopherson , 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 MANUALSEL 5.15 7/7] KVM: LAPIC: Enable timer posted-interrupt only when mwait/hlt is advertised Date: Wed, 27 Apr 2022 11:54:27 -0400 Message-Id: <20220427155431.19458-7-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220427155431.19458-1-sashal@kernel.org> References: <20220427155431.19458-1-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 1714a4eb6fb0cb79f182873cd011a8ed60ac65e8 ] As commit 0c5f81dad46 ("KVM: LAPIC: Inject timer interrupt via posted interrupt") mentioned that the host admin should well tune the guest setup, so that vCPUs are placed on isolated pCPUs, and with several pCPUs surplus for *busy* housekeeping. In this setup, it is preferrable to disable mwait/hlt/pause vmexits to keep the vCPUs in non-root mode. However, if only some guests isolated and others not, they would not have any benefit from posted timer interrupts, and at the same time lose VMX preemption timer fast paths because kvm_can_post_timer_interrupt() returns true and therefore forces kvm_can_use_hv_timer() to false. By guaranteeing that posted-interrupt timer is only used if MWAIT or HLT are done without vmexit, KVM can make a better choice and use the VMX preemption timer and the corresponding fast paths. Reported-by: Aili Yao Reviewed-by: Sean Christopherson Cc: Aili Yao Cc: Sean Christopherson Signed-off-by: Wanpeng Li Message-Id: <1643112538-36743-1-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- arch/x86/kvm/lapic.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 83d1743a1dd0..493d636e6231 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -113,7 +113,8 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic) static bool kvm_can_post_timer_interrupt(struct kvm_vcpu *vcpu) { - return pi_inject_timer && kvm_vcpu_apicv_active(vcpu); + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) && + (kvm_mwait_in_guest(vcpu->kvm) || kvm_hlt_in_guest(vcpu->kvm)); } bool kvm_can_use_hv_timer(struct kvm_vcpu *vcpu) -- 2.35.1