x86/speculation: Use synthetic bits for IBRS/IBPB/STIBP

Intel and AMD have different CPUID bits hence for those use synthetic bits
which get set on the respective vendor's in init_speculation_control(). So
that debacles like what the commit message of

  c65732e4 ("x86/cpu: Restore CPUID_8000_0008_EBX reload")

talks about don't happen anymore.
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Jörg Otte <jrg.otte@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Link: https://lkml.kernel.org/r/20180504161815.GG9257@pd.tnic

CVE-2018-3639 (x86)

(backported from commit e7c587da)
[smb: dropped guest_cpuid_has checks in svm.c and vmx.c]
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/include/asm/cpufeatures.h

@@ -199,12 +199,16 @@
 #define X86_FEATURE_INTEL_PT	( 7*32+15) /* Intel Processor Trace */
 #define X86_FEATURE_RSB_CTXSW	( 7*32+19) /* "" Fill RSB on context switches */
 
-/* Because the ALTERNATIVE scheme is for members of the X86_FEATURE club... */
-#define X86_FEATURE_KAISER     ( 7*32+31) /* CONFIG_PAGE_TABLE_ISOLATION w/o nokaiser */
-
 #define X86_FEATURE_USE_IBPB	( 7*32+21) /* "" Indirect Branch Prediction Barrier enabled */
+
 #define X86_FEATURE_SPEC_STORE_BYPASS_DISABLE	( 7*32+23) /* "" Disable Speculative Store Bypass. */
 #define X86_FEATURE_AMD_SSBD		( 7*32+24)  /* "" AMD SSBD implementation */
+#define X86_FEATURE_IBRS		( 7*32+25) /* Indirect Branch Restricted Speculation */
+#define X86_FEATURE_IBPB		( 7*32+26) /* Indirect Branch Prediction Barrier */
+#define X86_FEATURE_STIBP		( 7*32+27) /* Single Thread Indirect Branch Predictors */
+
+/* Because the ALTERNATIVE scheme is for members of the X86_FEATURE club... */
+#define X86_FEATURE_KAISER		( 7*32+31) /* CONFIG_PAGE_TABLE_ISOLATION w/o nokaiser */
 
 /* Virtualization flags: Linux defined, word 8 */
 #define X86_FEATURE_TPR_SHADOW  ( 8*32+ 0) /* Intel TPR Shadow */
@@ -258,9 +262,9 @@
 
 /* AMD-defined CPU features, CPUID level 0x80000008 (ebx), word 13 */
 #define X86_FEATURE_CLZERO	(13*32+0) /* CLZERO instruction */
-#define X86_FEATURE_IBPB	(13*32+12) /* Indirect Branch Prediction Barrier */
-#define X86_FEATURE_IBRS	(13*32+14) /* Indirect Branch Restricted Speculation */
-#define X86_FEATURE_STIBP	(13*32+15) /* Single Thread Indirect Branch Predictors */
+#define X86_FEATURE_AMD_IBPB	(13*32+12) /* "" Indirect Branch Prediction Barrier */
+#define X86_FEATURE_AMD_IBRS	(13*32+14) /* "" Indirect Branch Restricted Speculation */
+#define X86_FEATURE_AMD_STIBP	(13*32+15) /* "" Single Thread Indirect Branch Predictors */
 
 /* Thermal and Power Management Leaf, CPUID level 0x00000006 (eax), word 14 */
 #define X86_FEATURE_DTHERM	(14*32+ 0) /* Digital Thermal Sensor */

arch/x86/kernel/cpu/common.c

@@ -683,17 +683,23 @@ static void init_speculation_control(struct cpuinfo_x86 *c)
 	 * and they also have a different bit for STIBP support. Also,
 	 * a hypervisor might have set the individual AMD bits even on
 	 * Intel CPUs, for finer-grained selection of what's available.
-	 *
-	 * We use the AMD bits in 0x8000_0008 EBX as the generic hardware
-	 * features, which are visible in /proc/cpuinfo and used by the
-	 * kernel. So set those accordingly from the Intel bits.
 	 */
 	if (cpu_has(c, X86_FEATURE_SPEC_CTRL)) {
 		set_cpu_cap(c, X86_FEATURE_IBRS);
 		set_cpu_cap(c, X86_FEATURE_IBPB);
 	}
+
 	if (cpu_has(c, X86_FEATURE_INTEL_STIBP))
 		set_cpu_cap(c, X86_FEATURE_STIBP);
+
+	if (cpu_has(c, X86_FEATURE_AMD_IBRS))
+		set_cpu_cap(c, X86_FEATURE_IBRS);
+
+	if (cpu_has(c, X86_FEATURE_AMD_IBPB))
+		set_cpu_cap(c, X86_FEATURE_IBPB);
+
+	if (cpu_has(c, X86_FEATURE_AMD_STIBP))
+		set_cpu_cap(c, X86_FEATURE_STIBP);
 }
 
 void get_cpu_cap(struct cpuinfo_x86 *c)

arch/x86/kvm/cpuid.c

@@ -367,7 +367,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 
 	/* cpuid 0x80000008.0.ebx */
 	const u32 kvm_cpuid_80000008_0_ebx_x86_features =
-		F(IBPB);
+		F(AMD_IBPB) | F(AMD_IBRS);
 
 	/* all calls to cpuid_count() should be made on the same cpu */
 	get_cpu();
@@ -597,6 +597,11 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 		if (!g_phys_as)
 			g_phys_as = phys_as;
 		entry->eax = g_phys_as | (virt_as << 8);
+		/* IBRS and IBPB aren't necessarily present in hardware cpuid */
+		if (boot_cpu_has(X86_FEATURE_AMD_IBPB))
+			entry->ebx |= F(AMD_IBPB);
+		if (boot_cpu_has(X86_FEATURE_AMD_IBRS))
+			entry->ebx |= F(AMD_IBRS);
 		entry->ebx &= kvm_cpuid_80000008_0_ebx_x86_features;
 		cpuid_mask(&entry->ebx, CPUID_8000_0008_EBX);
 		entry->edx = 0;