x86/speculation: Use IBRS if available before calling into firmware

[linux-2.6-microblaze.git] / arch / x86 / include / asm / nospec-branch.h

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index af34b1e..ec90c32 100644 (file)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -219,17 +219,38 @@ static inline void vmexit_fill_RSB(void)
 #endif
 }
 
+#define alternative_msr_write(_msr, _val, _feature)            \
+       asm volatile(ALTERNATIVE("",                            \
+                                "movl %[msr], %%ecx\n\t"       \
+                                "movl %[val], %%eax\n\t"       \
+                                "movl $0, %%edx\n\t"           \
+                                "wrmsr",                       \
+                                _feature)                      \
+                    : : [msr] "i" (_msr), [val] "i" (_val)     \
+                    : "eax", "ecx", "edx", "memory")
+
 static inline void indirect_branch_prediction_barrier(void)
 {
-       asm volatile(ALTERNATIVE("",
-                                "movl %[msr], %%ecx\n\t"
-                                "movl %[val], %%eax\n\t"
-                                "movl $0, %%edx\n\t"
-                                "wrmsr",
-                                X86_FEATURE_USE_IBPB)
-                    : : [msr] "i" (MSR_IA32_PRED_CMD),
-                        [val] "i" (PRED_CMD_IBPB)
-                    : "eax", "ecx", "edx", "memory");
+       alternative_msr_write(MSR_IA32_PRED_CMD, PRED_CMD_IBPB,
+                             X86_FEATURE_USE_IBPB);
+}
+
+/*
+ * With retpoline, we must use IBRS to restrict branch prediction
+ * before calling into firmware.
+ */
+static inline void firmware_restrict_branch_speculation_start(void)
+{
+       preempt_disable();
+       alternative_msr_write(MSR_IA32_SPEC_CTRL, SPEC_CTRL_IBRS,
+                             X86_FEATURE_USE_IBRS_FW);
+}
+
+static inline void firmware_restrict_branch_speculation_end(void)
+{
+       alternative_msr_write(MSR_IA32_SPEC_CTRL, 0,
+                             X86_FEATURE_USE_IBRS_FW);
+       preempt_enable();
 }
 
 #endif /* __ASSEMBLY__ */