x86/speculation, KVM: Implement support for VIRT_SPEC_CTRL/LS_CFG

x86/speculation, KVM: Implement support for VIRT_SPEC_CTRL/LS_CFG

Add the necessary logic for supporting the emulated VIRT_SPEC_CTRL MSR to
x86_virt_spec_ctrl().  If either X86_FEATURE_LS_CFG_SSBD or
X86_FEATURE_VIRT_SPEC_CTRL is set then use the new guest_virt_spec_ctrl
argument to check whether the state must be modified on the host. The
update reuses speculative_store_bypass_update() so the ZEN-specific sibling
coordination can be reused.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Orabug: 28063992
CVE: CVE-2018-3639

(cherry picked from commit 47c61b39)
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/spec-ctrl.h
	arch/x86/kernel/cpu/bugs.c
[
bugs.c: different file name
spec-ctrl.h: contextual changes. Diff couldn't be applied
]

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