From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755279AbbHBAfr (ORCPT ); Sat, 1 Aug 2015 20:35:47 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:36771 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754517AbbHBAeb (ORCPT ); Sat, 1 Aug 2015 20:34:31 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Venkatesh Srinivas" , "Paolo Bonzini" , "Ben Serebrin" Date: Sun, 02 Aug 2015 01:02:37 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 050/164] KVM: VMX: Preserve host CR4.MCE value while in guest mode. In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.249 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.70-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Ben Serebrin commit 085e68eeafbf76e21848ad5bafaecec88a11dd64 upstream. The host's decision to enable machine check exceptions should remain in force during non-root mode. KVM was writing 0 to cr4 on VCPU reset and passed a slightly-modified 0 to the vmcs.guest_cr4 value. Tested: Built. On earlier version, tested by injecting machine check while a guest is spinning. Before the change, if guest CR4.MCE==0, then the machine check is escalated to Catastrophic Error (CATERR) and the machine dies. If guest CR4.MCE==1, then the machine check causes VMEXIT and is handled normally by host Linux. After the change, injecting a machine check causes normal Linux machine check handling. Signed-off-by: Ben Serebrin Reviewed-by: Venkatesh Srinivas Signed-off-by: Paolo Bonzini [bwh: Backported to 3.2: use read_cr4() instead of cr4_read_shadow()] Signed-off-by: Ben Hutchings --- arch/x86/kvm/vmx.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3032,8 +3032,16 @@ static void vmx_set_cr3(struct kvm_vcpu static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) { - unsigned long hw_cr4 = cr4 | (to_vmx(vcpu)->rmode.vm86_active ? - KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON); + /* + * Pass through host's Machine Check Enable value to hw_cr4, which + * is in force while we are in guest mode. Do not let guests control + * this bit, even if host CR4.MCE == 0. + */ + unsigned long hw_cr4 = + (read_cr4() & X86_CR4_MCE) | + (cr4 & ~X86_CR4_MCE) | + (to_vmx(vcpu)->rmode.vm86_active ? + KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON); if (cr4 & X86_CR4_VMXE) { /*