x86/kvm: Expose X86_FEATURE_MD_CLEAR to guests

X86_FEATURE_MD_CLEAR is a new CPUID bit which is set when microcode
provides the mechanism to invoke a flush of various exploitable CPU buffers
by invoking the VERW instruction.

Hand it through to guests so they can adjust their mitigations.

This also requires corresponding qemu changes, which are available
separately.

[ tglx: Massaged changelog ]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Jon Masters <jcm@redhat.com>
Tested-by: Jon Masters <jcm@redhat.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index c07958b59f5051d525ddf3e110412f9377ac5e96..39501e7afdb49dbb340095c418a9f3e1056c360e 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -410,7 +410,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
        /* cpuid 7.0.edx*/
        const u32 kvm_cpuid_7_0_edx_x86_features =
                F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
-               F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP);
+               F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
+               F(MD_CLEAR);
 
        /* all calls to cpuid_count() should be made on the same cpu */
        get_cpu();