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

[mirror_ubuntu-artful-kernel.git] / arch / x86 / kernel / cpu / bugs.c

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 050af4672ca008aa84c61f23b162b98b18d4b52e..7e5db5aa37f30e8817298af3ef0b0399075c8cdc 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -157,6 +157,36 @@ x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest)
                        wrmsrl(MSR_IA32_SPEC_CTRL, msrval);
                }
        }
+
+       /*
+        * If SSBD is not handled in MSR_SPEC_CTRL on AMD, update
+        * MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported.
+        */
+       if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&
+           !static_cpu_has(X86_FEATURE_VIRT_SSBD))
+               return;
+
+       /*
+        * If the host has SSBD mitigation enabled, force it in the host's
+        * virtual MSR value. If its not permanently enabled, evaluate
+        * current's TIF_SSBD thread flag.
+        */
+       if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE))
+               hostval = SPEC_CTRL_SSBD;
+       else
+               hostval = ssbd_tif_to_spec_ctrl(ti->flags);
+
+       /* Sanitize the guest value */
+       guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD;
+
+       if (hostval != guestval) {
+               unsigned long tif;
+
+               tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) :
+                                ssbd_spec_ctrl_to_tif(hostval);
+
+               speculative_store_bypass_update(tif);
+       }
 }
 EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl);