KVM: SVM: Implement VIRT_SPEC_CTRL support for SSBD

KVM: SVM: Implement VIRT_SPEC_CTRL support for SSBD

Expose the new virtualized architectural mechanism, VIRT_SSBD, for using
speculative store bypass disable (SSBD) under SVM.  This will allow guests
to use SSBD on hardware that uses non-architectural mechanisms for enabling
SSBD.

[ tglx: Folded the migration fixup from Paolo Bonzini ]

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Orabug: 28063992
CVE: CVE-2018-3639

(cherry picked from commit bc226f07)
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Conflicts:
	arch/x86/include/asm/kvm_host.h
	arch/x86/kernel/cpu/common.c
	arch/x86/kvm/cpuid.c
	arch/x86/kvm/svm.c
	arch/x86/kvm/vmx.c
	arch/x86/kvm/x86.c
[
We did not have cpu_has_high_real_mode_segbase entry at all.
Also msr_info is not in this patchset, I will take care of it
in Orabug: 28069548 in a future patchset.
]

Signed-off-by: Brian Maly <brian.maly@oracle.com>