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>
CVE-2018-3639 (x86)

(cherry-picked from commit 47c61b3955cf712cadfc25635bf9bc174af030ea)
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>