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 X-Spam-Level: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 230A2C4708F for ; Mon, 31 May 2021 14:23:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C6E5613D7 for ; Mon, 31 May 2021 14:23:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233757AbhEaOZW (ORCPT ); Mon, 31 May 2021 10:25:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:55082 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232307AbhEaNvO (ORCPT ); Mon, 31 May 2021 09:51:14 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A37EB613EA; Mon, 31 May 2021 13:32:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1622467938; bh=JZciasEvEPmMhPJ2Yltw5AYj7KSxC5rV+XIOgYsS43U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yx1aN+ECmWH84CDjMx3R4Ke2eMuzkYSrLThSeM5UyPAidaBVsAXUGHGt196NVtdyp 87/ZLETbAIxpEHFnvdPKVN7ER1TRPbHPqON9v6e5aDGPStlk9klpU2jA6aOBVRdhJ1 b39Rc2N5FmTg0eeSLds+ckx5jpuSX3ly7t11BAT0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sean Christopherson , Wanpeng Li , Paolo Bonzini Subject: [PATCH 5.10 057/252] KVM: X86: Fix vCPU preempted state from guests point of view Date: Mon, 31 May 2021 15:12:02 +0200 Message-Id: <20210531130659.917507144@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210531130657.971257589@linuxfoundation.org> References: <20210531130657.971257589@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li commit 1eff0ada88b48e4ac1e3fe26483b3684fedecd27 upstream. Commit 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's CPUID) avoids to access pv tlb shootdown host side logic when this pv feature is not exposed to guest, however, kvm_steal_time.preempted not only leveraged by pv tlb shootdown logic but also mitigate the lock holder preemption issue. >>From guest's point of view, vCPU is always preempted since we lose the reset of kvm_steal_time.preempted before vmentry if pv tlb shootdown feature is not exposed. This patch fixes it by clearing kvm_steal_time.preempted before vmentry. Fixes: 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's CPUID) Reviewed-by: Sean Christopherson Cc: stable@vger.kernel.org Signed-off-by: Wanpeng Li Message-Id: <1621339235-11131-3-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3006,6 +3006,8 @@ static void record_steal_time(struct kvm st->preempted & KVM_VCPU_FLUSH_TLB); if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB) kvm_vcpu_flush_tlb_guest(vcpu); + } else { + st->preempted = 0; } vcpu->arch.st.preempted = 0;