From: Ben Serebrin <[email protected]> This patch has been added to the 3.18 stable tree. If you have any objections, please let us know.
=============== [ Upstream commit 085e68eeafbf76e21848ad5bafaecec88a11dd64 ] 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 <[email protected]> Reviewed-by: Venkatesh Srinivas <[email protected]> Cc: [email protected] Signed-off-by: Paolo Bonzini <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- arch/x86/kvm/vmx.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index c7904b5..0d7f1dc 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3553,8 +3553,16 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) 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 = + (cr4_read_shadow() & 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) { /* -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in
