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[209.132.180.67]) by mx.google.com with ESMTP id gn23si4623061plb.19.2019.02.21.06.18.02; Thu, 21 Feb 2019 06:18:17 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=gNUii4OJ; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728180AbfBUOPf (ORCPT + 99 others); Thu, 21 Feb 2019 09:15:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:47212 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725880AbfBUOPe (ORCPT ); Thu, 21 Feb 2019 09:15:34 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 951902070B; Thu, 21 Feb 2019 14:15:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550758533; bh=RS7g4KO7o5BM0WXTu8njXOeY8w47moJrOYGKOrZuemY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gNUii4OJWfKagw+F6lWfkyMShw3eFXZhncrdjte7eJsvkp3ukJFi2BtzD3XDvSXtC tsL/0qSOS0lmeOGwr2gski1ZXyxdR3eCd/W/r8PJnmJxdIN0NQp2OMgtdl00/pRP+T LGGV1FaVTKLCbyA2bKrFKFRg+2Vaomy8gJXHBYOI= Date: Thu, 21 Feb 2019 15:15:30 +0100 From: Greg Kroah-Hartman To: Joerg Roedel Cc: stable@vger.kernel.org, Ben Hutchings , David Woodhouse , Paolo Bonzini , Jim Mattson , linux-kernel@vger.kernel.org, Joerg Roedel Subject: Re: [PATCH stable-4.4.y] KVM: VMX: Fix x2apic check in vmx_msr_bitmap_mode() Message-ID: <20190221141530.GA18436@kroah.com> References: <20190221135213.23926-1-joro@8bytes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190221135213.23926-1-joro@8bytes.org> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 21, 2019 at 02:52:13PM +0100, Joerg Roedel wrote: > From: Joerg Roedel > > The stable backport of upstream commit > > 904e14fb7cb96 KVM: VMX: make MSR bitmaps per-VCPU > > has a bug in vmx_msr_bitmap_mode(). It enables the x2apic > MSR-bitmap when the kernel emulates x2apic for the guest in > software. The upstream version of the commit checkes whether > the hardware has virtualization enabled for x2apic > emulation. > > Since KVM emulates x2apic for guests even when the host does > not support x2apic in hardware, this causes the intercept of > at least the X2APIC_TASKPRI MSR to be disabled on machines > not supporting that MSR. The result is undefined behavior, > on some machines (Intel Westmere based) it causes a crash of > the guest kernel when it tries to access that MSR. > > Change the check in vmx_msr_bitmap_mode() to match the upstream > code. This fixes the guest crashes observed with stable > kernels starting with v4.4.168 through v4.4.175. > > Signed-off-by: Joerg Roedel > --- > arch/x86/kvm/vmx.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index aee2886a387c..14553f6c03a6 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -4628,7 +4628,9 @@ static u8 vmx_msr_bitmap_mode(struct kvm_vcpu *vcpu) > { > u8 mode = 0; > > - if (irqchip_in_kernel(vcpu->kvm) && apic_x2apic_mode(vcpu->arch.apic)) { > + if (cpu_has_secondary_exec_ctrls() && > + (vmcs_read32(SECONDARY_VM_EXEC_CONTROL) & > + SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE)) { > mode |= MSR_BITMAP_MODE_X2APIC; > if (enable_apicv) > mode |= MSR_BITMAP_MODE_X2APIC_APICV; > -- > 2.16.3 > Ugh, good catch! Any hint as to what type of testing that you did that caught this? I keep asking people to run some kvm tests, but so far no one is :( thanks, greg k-h