x86/vmscape: Enumerate VMSCAPE bug

The VMSCAPE vulnerability may allow a guest to cause Branch Target
Injection (BTI) in userspace hypervisors.

Kernels (both host and guest) have existing defenses against direct BTI
attacks from guests. There are also inter-process BTI mitigations which
prevent processes from attacking each other. However, the threat in this
case is to a userspace hypervisor within the same process as the attacker.

Userspace hypervisors have access to their own sensitive data like disk
encryption keys and also typically have access to all guest data. This
means guest userspace may use the hypervisor as a confused deputy to attack
sensitive guest kernel data. There are no existing mitigations for these
attacks.

Introduce X86_BUG_VMSCAPE for this vulnerability and set it on affected
Intel and AMD CPUs.

Signed-off-by: Pawan Gupta <[e-mail]>
Signed-off-by: Dave Hansen <[e-mail]>
Reviewed-by: Borislav Petkov (AMD) <[e-mail]>

arch/x86/include/asm/cpufeatures.h

···
 #define X86_BUG_ITS			X86_BUG( 1*32+ 7) /* "its" CPU is affected by Indirect Target Selection */
 #define X86_BUG_ITS_NATIVE_ONLY		X86_BUG( 1*32+ 8) /* "its_native_only" CPU is affected by ITS, VMX is not affected */
 #define X86_BUG_TSA			X86_BUG( 1*32+ 9) /* "tsa" CPU is affected by Transient Scheduler Attacks */
+#define X86_BUG_VMSCAPE			X86_BUG( 1*32+10) /* "vmscape" CPU is affected by VMSCAPE attacks from guests */
 #endif /* _ASM_X86_CPUFEATURES_H */

arch/x86/kernel/cpu/common.c

···
 #define ITS_NATIVE_ONLY	BIT(9)
 /* CPU is affected by Transient Scheduler Attacks */
 #define TSA		BIT(10)
+/* CPU is affected by VMSCAPE */
+#define VMSCAPE		BIT(11)
 
 static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
 	VULNBL_INTEL_STEPS(INTEL_IVYBRIDGE,	     X86_STEP_MAX,	SRBDS),
···
 	VULNBL_INTEL_STEPS(INTEL_BROADWELL_G,	     X86_STEP_MAX,	SRBDS),
 	VULNBL_INTEL_STEPS(INTEL_BROADWELL_X,	     X86_STEP_MAX,	MMIO),
 	VULNBL_INTEL_STEPS(INTEL_BROADWELL,	     X86_STEP_MAX,	SRBDS),
-	VULNBL_INTEL_STEPS(INTEL_SKYLAKE_X,		      0x5,	MMIO | RETBLEED | GDS),
-	VULNBL_INTEL_STEPS(INTEL_SKYLAKE_X,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | ITS),
-	VULNBL_INTEL_STEPS(INTEL_SKYLAKE_L,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | SRBDS),
-	VULNBL_INTEL_STEPS(INTEL_SKYLAKE,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | SRBDS),
-	VULNBL_INTEL_STEPS(INTEL_KABYLAKE_L,		      0xb,	MMIO | RETBLEED | GDS | SRBDS),
-	VULNBL_INTEL_STEPS(INTEL_KABYLAKE_L,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | SRBDS | ITS),
-	VULNBL_INTEL_STEPS(INTEL_KABYLAKE,		      0xc,	MMIO | RETBLEED | GDS | SRBDS),
-	VULNBL_INTEL_STEPS(INTEL_KABYLAKE,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | SRBDS | ITS),
-	VULNBL_INTEL_STEPS(INTEL_CANNONLAKE_L,	     X86_STEP_MAX,	RETBLEED),
+	VULNBL_INTEL_STEPS(INTEL_SKYLAKE_X,		      0x5,	MMIO | RETBLEED | GDS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_SKYLAKE_X,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | ITS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_SKYLAKE_L,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_SKYLAKE,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_KABYLAKE_L,		      0xb,	MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_KABYLAKE_L,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | SRBDS | ITS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_KABYLAKE,		      0xc,	MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_KABYLAKE,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | SRBDS | ITS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_CANNONLAKE_L,	     X86_STEP_MAX,	RETBLEED | VMSCAPE),
 	VULNBL_INTEL_STEPS(INTEL_ICELAKE_L,	     X86_STEP_MAX,	MMIO | MMIO_SBDS | RETBLEED | GDS | ITS | ITS_NATIVE_ONLY),
 	VULNBL_INTEL_STEPS(INTEL_ICELAKE_D,	     X86_STEP_MAX,	MMIO | GDS | ITS | ITS_NATIVE_ONLY),
 	VULNBL_INTEL_STEPS(INTEL_ICELAKE_X,	     X86_STEP_MAX,	MMIO | GDS | ITS | ITS_NATIVE_ONLY),
-	VULNBL_INTEL_STEPS(INTEL_COMETLAKE,	     X86_STEP_MAX,	MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
-	VULNBL_INTEL_STEPS(INTEL_COMETLAKE_L,		      0x0,	MMIO | RETBLEED | ITS),
-	VULNBL_INTEL_STEPS(INTEL_COMETLAKE_L,	     X86_STEP_MAX,	MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
+	VULNBL_INTEL_STEPS(INTEL_COMETLAKE,	     X86_STEP_MAX,	MMIO | MMIO_SBDS | RETBLEED | GDS | ITS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_COMETLAKE_L,		      0x0,	MMIO | RETBLEED | ITS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_COMETLAKE_L,	     X86_STEP_MAX,	MMIO | MMIO_SBDS | RETBLEED | GDS | ITS | VMSCAPE),
 	VULNBL_INTEL_STEPS(INTEL_TIGERLAKE_L,	     X86_STEP_MAX,	GDS | ITS | ITS_NATIVE_ONLY),
 	VULNBL_INTEL_STEPS(INTEL_TIGERLAKE,	     X86_STEP_MAX,	GDS | ITS | ITS_NATIVE_ONLY),
 	VULNBL_INTEL_STEPS(INTEL_LAKEFIELD,	     X86_STEP_MAX,	MMIO | MMIO_SBDS | RETBLEED),
 	VULNBL_INTEL_STEPS(INTEL_ROCKETLAKE,	     X86_STEP_MAX,	MMIO | RETBLEED | GDS | ITS | ITS_NATIVE_ONLY),
-	VULNBL_INTEL_TYPE(INTEL_ALDERLAKE,		     ATOM,	RFDS),
-	VULNBL_INTEL_STEPS(INTEL_ALDERLAKE_L,	     X86_STEP_MAX,	RFDS),
-	VULNBL_INTEL_TYPE(INTEL_RAPTORLAKE,		     ATOM,	RFDS),
-	VULNBL_INTEL_STEPS(INTEL_RAPTORLAKE_P,	     X86_STEP_MAX,	RFDS),
-	VULNBL_INTEL_STEPS(INTEL_RAPTORLAKE_S,	     X86_STEP_MAX,	RFDS),
-	VULNBL_INTEL_STEPS(INTEL_ATOM_GRACEMONT,     X86_STEP_MAX,	RFDS),
+	VULNBL_INTEL_TYPE(INTEL_ALDERLAKE,		     ATOM,	RFDS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_ALDERLAKE,	     X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_ALDERLAKE_L,	     X86_STEP_MAX,	RFDS | VMSCAPE),
+	VULNBL_INTEL_TYPE(INTEL_RAPTORLAKE,		     ATOM,	RFDS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_RAPTORLAKE,	     X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_RAPTORLAKE_P,	     X86_STEP_MAX,	RFDS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_RAPTORLAKE_S,	     X86_STEP_MAX,	RFDS | VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_METEORLAKE_L,	     X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_ARROWLAKE_H,	     X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_ARROWLAKE,	     X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_ARROWLAKE_U,	     X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_LUNARLAKE_M,	     X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_SAPPHIRERAPIDS_X,   X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_GRANITERAPIDS_X,    X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_EMERALDRAPIDS_X,    X86_STEP_MAX,	VMSCAPE),
+	VULNBL_INTEL_STEPS(INTEL_ATOM_GRACEMONT,     X86_STEP_MAX,	RFDS | VMSCAPE),
 	VULNBL_INTEL_STEPS(INTEL_ATOM_TREMONT,	     X86_STEP_MAX,	MMIO | MMIO_SBDS | RFDS),
 	VULNBL_INTEL_STEPS(INTEL_ATOM_TREMONT_D,     X86_STEP_MAX,	MMIO | RFDS),
 	VULNBL_INTEL_STEPS(INTEL_ATOM_TREMONT_L,     X86_STEP_MAX,	MMIO | MMIO_SBDS | RFDS),
 	VULNBL_INTEL_STEPS(INTEL_ATOM_GOLDMONT,      X86_STEP_MAX,	RFDS),
 	VULNBL_INTEL_STEPS(INTEL_ATOM_GOLDMONT_D,    X86_STEP_MAX,	RFDS),
 	VULNBL_INTEL_STEPS(INTEL_ATOM_GOLDMONT_PLUS, X86_STEP_MAX,	RFDS),
+	VULNBL_INTEL_STEPS(INTEL_ATOM_CRESTMONT_X,   X86_STEP_MAX,	VMSCAPE),
 
 	VULNBL_AMD(0x15, RETBLEED),
 	VULNBL_AMD(0x16, RETBLEED),
-	VULNBL_AMD(0x17, RETBLEED | SMT_RSB | SRSO),
-	VULNBL_HYGON(0x18, RETBLEED | SMT_RSB | SRSO),
-	VULNBL_AMD(0x19, SRSO | TSA),
-	VULNBL_AMD(0x1a, SRSO),
+	VULNBL_AMD(0x17, RETBLEED | SMT_RSB | SRSO | VMSCAPE),
+	VULNBL_HYGON(0x18, RETBLEED | SMT_RSB | SRSO | VMSCAPE),
+	VULNBL_AMD(0x19, SRSO | TSA | VMSCAPE),
+	VULNBL_AMD(0x1a, SRSO | VMSCAPE),
 	{}
 };
 
···
 				setup_force_cpu_bug(X86_BUG_TSA);
 		}
 	}
+
+	/*
+	 * Set the bug only on bare-metal. A nested hypervisor should already be
+	 * deploying IBPB to isolate itself from nested guests.
+	 */
+	if (cpu_matches(cpu_vuln_blacklist, VMSCAPE) &&
+	    !boot_cpu_has(X86_FEATURE_HYPERVISOR))
+		setup_force_cpu_bug(X86_BUG_VMSCAPE);
 
 	if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
 		return;