Hi Ben, On Thu, Apr 16, 2015 at 11:58:05AM -0700, Ben Serebrin wrote: >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.
Could you point out which section of SDM describes that the machine check is escalated to a CATERR if CR4.MCE==0? Regards, Wanpeng Li >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]> >--- > 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 f5e8dce..f7b6168 100644 >--- a/arch/x86/kvm/vmx.c >+++ b/arch/x86/kvm/vmx.c >@@ -3622,8 +3622,16 @@ 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) { > /* >-- >2.2.0.rc0.207.ga3a616c > >-- >To unsubscribe from this list: send the line "unsubscribe kvm" in >the body of a message to [email protected] >More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
