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x86/its: Enumerate Indirect Target Selection (ITS) bug

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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>
This commit is contained in:
Pawan Gupta 2024-06-21 17:40:41 -07:00 • committed by Dave Hansen
parent 1ac116ce64
commit 159013a7ca
4 changed files with 58 additions and 13 deletions
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1
arch/x86/include/asm/cpufeatures.h
View file

@ -533,4 +533,5 @@
#define X86_BUG_BHI X86_BUG(1*32 + 3) /* "bhi" 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_SPECTRE_V2_USER X86_BUG(1*32 + 5) /* "spectre_v2_user" CPU is affected by Spectre variant 2 attack between user processes */
#define X86_BUG_ITS X86_BUG(1*32 + 6) /* "its" CPU is affected by Indirect Target Selection */
#endif /* _ASM_X86_CPUFEATURES_H */

8
arch/x86/include/asm/msr-index.h
View file

@ -211,6 +211,14 @@
* 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 MSR_IA32_FLUSH_CMD 0x0000010b
#define L1D_FLUSH BIT(0) /*

58
arch/x86/kernel/cpu/common.c
View file

@ -1227,6 +1227,8 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
#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_STEPS(INTEL_IVYBRIDGE, X86_STEP_MAX, SRBDS),
@ -1238,22 +1240,25 @@ static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
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, X86_STEP_MAX, MMIO | RETBLEED | GDS),
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, X86_STEP_MAX, MMIO | RETBLEED | GDS | SRBDS),
VULNBL_INTEL_STEPS(INTEL_KABYLAKE, 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_ICELAKE_L, X86_STEP_MAX, MMIO | MMIO_SBDS | RETBLEED | GDS),
VULNBL_INTEL_STEPS(INTEL_ICELAKE_D, X86_STEP_MAX, MMIO | GDS),
VULNBL_INTEL_STEPS(INTEL_ICELAKE_X, X86_STEP_MAX, MMIO | GDS),
VULNBL_INTEL_STEPS(INTEL_COMETLAKE, X86_STEP_MAX, MMIO | MMIO_SBDS | RETBLEED | GDS),
VULNBL_INTEL_STEPS(INTEL_COMETLAKE_L, 0x0, MMIO | RETBLEED),
VULNBL_INTEL_STEPS(INTEL_COMETLAKE_L, X86_STEP_MAX, MMIO | MMIO_SBDS | RETBLEED | GDS),
VULNBL_INTEL_STEPS(INTEL_TIGERLAKE_L, X86_STEP_MAX, GDS),
VULNBL_INTEL_STEPS(INTEL_TIGERLAKE, X86_STEP_MAX, GDS),
VULNBL_INTEL_STEPS(INTEL_ICELAKE_L, X86_STEP_MAX, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
VULNBL_INTEL_STEPS(INTEL_ICELAKE_D, X86_STEP_MAX, MMIO | GDS | ITS),
VULNBL_INTEL_STEPS(INTEL_ICELAKE_X, X86_STEP_MAX, MMIO | GDS | ITS),
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_TIGERLAKE_L, X86_STEP_MAX, GDS | ITS),
VULNBL_INTEL_STEPS(INTEL_TIGERLAKE, X86_STEP_MAX, GDS | ITS),
VULNBL_INTEL_STEPS(INTEL_LAKEFIELD, X86_STEP_MAX, MMIO | MMIO_SBDS | RETBLEED),
VULNBL_INTEL_STEPS(INTEL_ROCKETLAKE, X86_STEP_MAX, MMIO | RETBLEED | GDS),
VULNBL_INTEL_STEPS(INTEL_ROCKETLAKE, X86_STEP_MAX, MMIO | RETBLEED | GDS | ITS),
VULNBL_INTEL_TYPE(INTEL_ALDERLAKE, ATOM, RFDS),
VULNBL_INTEL_STEPS(INTEL_ALDERLAKE_L, X86_STEP_MAX, RFDS),
VULNBL_INTEL_TYPE(INTEL_RAPTORLAKE, ATOM, RFDS),
@ -1318,6 +1323,32 @@ static bool __init vulnerable_to_rfds(u64 x86_arch_cap_msr)
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();
@ -1449,6 +1480,9 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
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;

4
arch/x86/kvm/x86.c
View file

@ -1584,7 +1584,7 @@ EXPORT_SYMBOL_GPL(kvm_emulate_rdpmc);
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)
{
@ -1618,6 +1618,8 @@ static u64 kvm_get_arch_capabilities(void)
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)) {
/*