From: Andi Kleen ak@linux.intel.com
commit 6c4dbbd14730c43f4ed808a9c42ca41625925c22 upstream.
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 [bwh: Backported to 4.4: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/cpuid.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -366,7 +366,7 @@ static inline int __do_cpuid_ent(struct /* cpuid 7.0.edx*/ const u32 kvm_cpuid_7_0_edx_x86_features = F(SPEC_CTRL) | F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | - F(INTEL_STIBP); + F(INTEL_STIBP) | F(MD_CLEAR);
/* all calls to cpuid_count() should be made on the same cpu */ get_cpu();