KVM: VMX: Preserve host CR4.MCE value while in guest mode.
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 <serebrin@google.com> Reviewed-by: Venkatesh Srinivas <venkateshs@google.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>