[PATCH 6.1 85/92] x86/its: Enumerate Indirect Target Selection (ITS) bug

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>

commit 159013a7ca18c271ff64192deb62a689b622d860 upstream.

ITS bug in some pre-Alderlake Intel CPUs may allow indirect branches in the
first half of a cache line get predicted to a target of a branch located in
the second half of the cache line.

Set X86_BUG_ITS on affected CPUs. Mitigation to follow in later commits.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/include/asm/cpufeatures.h |    1 
 arch/x86/include/asm/msr-index.h   |    8 +++++
 arch/x86/kernel/cpu/common.c       |   58 +++++++++++++++++++++++++++++--------
 arch/x86/kvm/x86.c                 |    4 +-
 4 files changed, 58 insertions(+), 13 deletions(-)

--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -495,4 +495,5 @@
 #define X86_BUG_RFDS			X86_BUG(1*32 + 2) /* CPU is vulnerable to Register File Data Sampling */
 #define X86_BUG_BHI			X86_BUG(1*32 + 3) /* CPU is affected by Branch History Injection */
 #define X86_BUG_IBPB_NO_RET		X86_BUG(1*32 + 4) /* "ibpb_no_ret" IBPB omits return target predictions */
+#define X86_BUG_ITS			X86_BUG(1*32 + 5) /* CPU is affected by Indirect Target Selection */
 #endif /* _ASM_X86_CPUFEATURES_H */
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -185,6 +185,14 @@
 						 * VERW clears CPU Register
 						 * File.
 						 */
+#define ARCH_CAP_ITS_NO			BIT_ULL(62) /*
+						     * Not susceptible to
+						     * Indirect Target Selection.
+						     * This bit is not set by
+						     * HW, but is synthesized by
+						     * VMMs for guests to know
+						     * their affected status.
+						     */
 
 #define ARCH_CAP_XAPIC_DISABLE		BIT(21)	/*
 						 * IA32_XAPIC_DISABLE_STATUS MSR
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1251,6 +1251,8 @@ static const __initconst struct x86_cpu_
 #define GDS		BIT(6)
 /* CPU is affected by Register File Data Sampling */
 #define RFDS		BIT(7)
+/* CPU is affected by Indirect Target Selection */
+#define ITS		BIT(8)
 
 static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
 	VULNBL_INTEL_STEPPINGS(IVYBRIDGE,	X86_STEPPING_ANY,		SRBDS),
@@ -1262,22 +1264,25 @@ static const struct x86_cpu_id cpu_vuln_
 	VULNBL_INTEL_STEPPINGS(BROADWELL_G,	X86_STEPPING_ANY,		SRBDS),
 	VULNBL_INTEL_STEPPINGS(BROADWELL_X,	X86_STEPPING_ANY,		MMIO),
 	VULNBL_INTEL_STEPPINGS(BROADWELL,	X86_STEPPING_ANY,		SRBDS),
-	VULNBL_INTEL_STEPPINGS(SKYLAKE_X,	X86_STEPPING_ANY,		MMIO | RETBLEED | GDS),
+	VULNBL_INTEL_STEPPINGS(SKYLAKE_X,	X86_STEPPINGS(0x0, 0x5),	MMIO | RETBLEED | GDS),
+	VULNBL_INTEL_STEPPINGS(SKYLAKE_X,	X86_STEPPING_ANY,		MMIO | RETBLEED | GDS | ITS),
 	VULNBL_INTEL_STEPPINGS(SKYLAKE_L,	X86_STEPPING_ANY,		MMIO | RETBLEED | GDS | SRBDS),
 	VULNBL_INTEL_STEPPINGS(SKYLAKE,		X86_STEPPING_ANY,		MMIO | RETBLEED | GDS | SRBDS),
-	VULNBL_INTEL_STEPPINGS(KABYLAKE_L,	X86_STEPPING_ANY,		MMIO | RETBLEED | GDS | SRBDS),
-	VULNBL_INTEL_STEPPINGS(KABYLAKE,	X86_STEPPING_ANY,		MMIO | RETBLEED | GDS | SRBDS),
+	VULNBL_INTEL_STEPPINGS(KABYLAKE_L,	X86_STEPPINGS(0x0, 0xb),	MMIO | RETBLEED | GDS | SRBDS),
+	VULNBL_INTEL_STEPPINGS(KABYLAKE_L,	X86_STEPPING_ANY,		MMIO | RETBLEED | GDS | SRBDS | ITS),
+	VULNBL_INTEL_STEPPINGS(KABYLAKE,	X86_STEPPINGS(0x0, 0xc),	MMIO | RETBLEED | GDS | SRBDS),
+	VULNBL_INTEL_STEPPINGS(KABYLAKE,	X86_STEPPING_ANY,		MMIO | RETBLEED | GDS | SRBDS | ITS),
 	VULNBL_INTEL_STEPPINGS(CANNONLAKE_L,	X86_STEPPING_ANY,		RETBLEED),
-	VULNBL_INTEL_STEPPINGS(ICELAKE_L,	X86_STEPPING_ANY,		MMIO | MMIO_SBDS | RETBLEED | GDS),
-	VULNBL_INTEL_STEPPINGS(ICELAKE_D,	X86_STEPPING_ANY,		MMIO | GDS),
-	VULNBL_INTEL_STEPPINGS(ICELAKE_X,	X86_STEPPING_ANY,		MMIO | GDS),
-	VULNBL_INTEL_STEPPINGS(COMETLAKE,	X86_STEPPING_ANY,		MMIO | MMIO_SBDS | RETBLEED | GDS),
-	VULNBL_INTEL_STEPPINGS(COMETLAKE_L,	X86_STEPPINGS(0x0, 0x0),	MMIO | RETBLEED),
-	VULNBL_INTEL_STEPPINGS(COMETLAKE_L,	X86_STEPPING_ANY,		MMIO | MMIO_SBDS | RETBLEED | GDS),
-	VULNBL_INTEL_STEPPINGS(TIGERLAKE_L,	X86_STEPPING_ANY,		GDS),
-	VULNBL_INTEL_STEPPINGS(TIGERLAKE,	X86_STEPPING_ANY,		GDS),
+	VULNBL_INTEL_STEPPINGS(ICELAKE_L,	X86_STEPPING_ANY,		MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
+	VULNBL_INTEL_STEPPINGS(ICELAKE_D,	X86_STEPPING_ANY,		MMIO | GDS | ITS),
+	VULNBL_INTEL_STEPPINGS(ICELAKE_X,	X86_STEPPING_ANY,		MMIO | GDS | ITS),
+	VULNBL_INTEL_STEPPINGS(COMETLAKE,	X86_STEPPING_ANY,		MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
+	VULNBL_INTEL_STEPPINGS(COMETLAKE_L,	X86_STEPPINGS(0x0, 0x0),	MMIO | RETBLEED | ITS),
+	VULNBL_INTEL_STEPPINGS(COMETLAKE_L,	X86_STEPPING_ANY,		MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
+	VULNBL_INTEL_STEPPINGS(TIGERLAKE_L,	X86_STEPPING_ANY,		GDS | ITS),
+	VULNBL_INTEL_STEPPINGS(TIGERLAKE,	X86_STEPPING_ANY,		GDS | ITS),
 	VULNBL_INTEL_STEPPINGS(LAKEFIELD,	X86_STEPPING_ANY,		MMIO | MMIO_SBDS | RETBLEED),
-	VULNBL_INTEL_STEPPINGS(ROCKETLAKE,	X86_STEPPING_ANY,		MMIO | RETBLEED | GDS),
+	VULNBL_INTEL_STEPPINGS(ROCKETLAKE,	X86_STEPPING_ANY,		MMIO | RETBLEED | GDS | ITS),
 	VULNBL_INTEL_STEPPINGS(ALDERLAKE,	X86_STEPPING_ANY,		RFDS),
 	VULNBL_INTEL_STEPPINGS(ALDERLAKE_L,	X86_STEPPING_ANY,		RFDS),
 	VULNBL_INTEL_STEPPINGS(RAPTORLAKE,	X86_STEPPING_ANY,		RFDS),
@@ -1341,6 +1346,32 @@ static bool __init vulnerable_to_rfds(u6
 	return cpu_matches(cpu_vuln_blacklist, RFDS);
 }
 
+static bool __init vulnerable_to_its(u64 x86_arch_cap_msr)
+{
+	/* The "immunity" bit trumps everything else: */
+	if (x86_arch_cap_msr & ARCH_CAP_ITS_NO)
+		return false;
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+		return false;
+
+	/* None of the affected CPUs have BHI_CTRL */
+	if (boot_cpu_has(X86_FEATURE_BHI_CTRL))
+		return false;
+
+	/*
+	 * If a VMM did not expose ITS_NO, assume that a guest could
+	 * be running on a vulnerable hardware or may migrate to such
+	 * hardware.
+	 */
+	if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
+		return true;
+
+	if (cpu_matches(cpu_vuln_blacklist, ITS))
+		return true;
+
+	return false;
+}
+
 static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
 {
 	u64 x86_arch_cap_msr = x86_read_arch_cap_msr();
@@ -1468,6 +1499,9 @@ static void __init cpu_set_bug_bits(stru
 	if (cpu_has(c, X86_FEATURE_AMD_IBPB) && !cpu_has(c, X86_FEATURE_AMD_IBPB_RET))
 		setup_force_cpu_bug(X86_BUG_IBPB_NO_RET);
 
+	if (vulnerable_to_its(x86_arch_cap_msr))
+		setup_force_cpu_bug(X86_BUG_ITS);
+
 	if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
 		return;
 
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1614,7 +1614,7 @@ static unsigned int num_msr_based_featur
 	 ARCH_CAP_PSCHANGE_MC_NO | ARCH_CAP_TSX_CTRL_MSR | ARCH_CAP_TAA_NO | \
 	 ARCH_CAP_SBDR_SSDP_NO | ARCH_CAP_FBSDP_NO | ARCH_CAP_PSDP_NO | \
 	 ARCH_CAP_FB_CLEAR | ARCH_CAP_RRSBA | ARCH_CAP_PBRSB_NO | ARCH_CAP_GDS_NO | \
-	 ARCH_CAP_RFDS_NO | ARCH_CAP_RFDS_CLEAR | ARCH_CAP_BHI_NO)
+	 ARCH_CAP_RFDS_NO | ARCH_CAP_RFDS_CLEAR | ARCH_CAP_BHI_NO | ARCH_CAP_ITS_NO)
 
 static u64 kvm_get_arch_capabilities(void)
 {
@@ -1653,6 +1653,8 @@ static u64 kvm_get_arch_capabilities(voi
 		data |= ARCH_CAP_MDS_NO;
 	if (!boot_cpu_has_bug(X86_BUG_RFDS))
 		data |= ARCH_CAP_RFDS_NO;
+	if (!boot_cpu_has_bug(X86_BUG_ITS))
+		data |= ARCH_CAP_ITS_NO;
 
 	if (!boot_cpu_has(X86_FEATURE_RTM)) {
 		/*