KVM: x86: Prevent host from panicking on shared MSR writes.

KVM: x86: Prevent host from panicking on shared MSR writes.

commit 8b3c3104c3f4f706e99365c3e0d2aa61b95f969f upstream.

The previous patch blocked invalid writes directly when the MSR
is written.  As a precaution, prevent future similar mistakes by
gracefulling handle GPs caused by writes to shared MSRs.

Signed-off-by: Andrew Honig <ahonig@google.com>
[Remove parts obsoleted by Nadav's patch. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>