diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches/bugfix/x86/gds/x86-speculation-add-gather-data-sampling-mitigation.patch | 562 |
1 files changed, 562 insertions, 0 deletions
diff --git a/debian/patches/bugfix/x86/gds/x86-speculation-add-gather-data-sampling-mitigation.patch b/debian/patches/bugfix/x86/gds/x86-speculation-add-gather-data-sampling-mitigation.patch new file mode 100644 index 000000000..c426811c6 --- /dev/null +++ b/debian/patches/bugfix/x86/gds/x86-speculation-add-gather-data-sampling-mitigation.patch @@ -0,0 +1,562 @@ +From d63b3f0e819275ee64648eb01330aad3e347d9ba Mon Sep 17 00:00:00 2001 +From: Daniel Sneddon <daniel.sneddon@linux.intel.com> +Date: Wed, 12 Jul 2023 19:43:11 -0700 +Subject: x86/speculation: Add Gather Data Sampling mitigation + +From: Daniel Sneddon <daniel.sneddon@linux.intel.com> + +commit 8974eb588283b7d44a7c91fa09fcbaf380339f3a upstream + +Gather Data Sampling (GDS) is a hardware vulnerability which allows +unprivileged speculative access to data which was previously stored in +vector registers. + +Intel processors that support AVX2 and AVX512 have gather instructions +that fetch non-contiguous data elements from memory. On vulnerable +hardware, when a gather instruction is transiently executed and +encounters a fault, stale data from architectural or internal vector +registers may get transiently stored to the destination vector +register allowing an attacker to infer the stale data using typical +side channel techniques like cache timing attacks. + +This mitigation is different from many earlier ones for two reasons. +First, it is enabled by default and a bit must be set to *DISABLE* it. +This is the opposite of normal mitigation polarity. This means GDS can +be mitigated simply by updating microcode and leaving the new control +bit alone. + +Second, GDS has a "lock" bit. This lock bit is there because the +mitigation affects the hardware security features KeyLocker and SGX. +It needs to be enabled and *STAY* enabled for these features to be +mitigated against GDS. + +The mitigation is enabled in the microcode by default. Disable it by +setting gather_data_sampling=off or by disabling all mitigations with +mitigations=off. The mitigation status can be checked by reading: + + /sys/devices/system/cpu/vulnerabilities/gather_data_sampling + +Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> +Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> +Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> +Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + Documentation/ABI/testing/sysfs-devices-system-cpu | 11 - + Documentation/admin-guide/hw-vuln/gather_data_sampling.rst | 99 +++++++++ + Documentation/admin-guide/hw-vuln/index.rst | 1 + Documentation/admin-guide/kernel-parameters.txt | 33 ++- + arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/msr-index.h | 11 + + arch/x86/kernel/cpu/bugs.c | 129 +++++++++++++ + arch/x86/kernel/cpu/common.c | 34 ++- + arch/x86/kernel/cpu/cpu.h | 1 + drivers/base/cpu.c | 8 + 10 files changed, 305 insertions(+), 23 deletions(-) + create mode 100644 Documentation/admin-guide/hw-vuln/gather_data_sampling.rst + +--- a/Documentation/ABI/testing/sysfs-devices-system-cpu ++++ b/Documentation/ABI/testing/sysfs-devices-system-cpu +@@ -472,16 +472,17 @@ Description: information about CPUs hete + cpu_capacity: capacity of cpu#. + + What: /sys/devices/system/cpu/vulnerabilities ++ /sys/devices/system/cpu/vulnerabilities/gather_data_sampling ++ /sys/devices/system/cpu/vulnerabilities/itlb_multihit ++ /sys/devices/system/cpu/vulnerabilities/l1tf ++ /sys/devices/system/cpu/vulnerabilities/mds + /sys/devices/system/cpu/vulnerabilities/meltdown ++ /sys/devices/system/cpu/vulnerabilities/mmio_stale_data ++ /sys/devices/system/cpu/vulnerabilities/spec_store_bypass + /sys/devices/system/cpu/vulnerabilities/spectre_v1 + /sys/devices/system/cpu/vulnerabilities/spectre_v2 +- /sys/devices/system/cpu/vulnerabilities/spec_store_bypass +- /sys/devices/system/cpu/vulnerabilities/l1tf +- /sys/devices/system/cpu/vulnerabilities/mds + /sys/devices/system/cpu/vulnerabilities/srbds + /sys/devices/system/cpu/vulnerabilities/tsx_async_abort +- /sys/devices/system/cpu/vulnerabilities/itlb_multihit +- /sys/devices/system/cpu/vulnerabilities/mmio_stale_data + Date: January 2018 + Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> + Description: Information about CPU vulnerabilities +--- /dev/null ++++ b/Documentation/admin-guide/hw-vuln/gather_data_sampling.rst +@@ -0,0 +1,99 @@ ++.. SPDX-License-Identifier: GPL-2.0 ++ ++GDS - Gather Data Sampling ++========================== ++ ++Gather Data Sampling is a hardware vulnerability which allows unprivileged ++speculative access to data which was previously stored in vector registers. ++ ++Problem ++------- ++When a gather instruction performs loads from memory, different data elements ++are merged into the destination vector register. However, when a gather ++instruction that is transiently executed encounters a fault, stale data from ++architectural or internal vector registers may get transiently forwarded to the ++destination vector register instead. This will allow a malicious attacker to ++infer stale data using typical side channel techniques like cache timing ++attacks. GDS is a purely sampling-based attack. ++ ++The attacker uses gather instructions to infer the stale vector register data. ++The victim does not need to do anything special other than use the vector ++registers. The victim does not need to use gather instructions to be ++vulnerable. ++ ++Because the buffers are shared between Hyper-Threads cross Hyper-Thread attacks ++are possible. ++ ++Attack scenarios ++---------------- ++Without mitigation, GDS can infer stale data across virtually all ++permission boundaries: ++ ++ Non-enclaves can infer SGX enclave data ++ Userspace can infer kernel data ++ Guests can infer data from hosts ++ Guest can infer guest from other guests ++ Users can infer data from other users ++ ++Because of this, it is important to ensure that the mitigation stays enabled in ++lower-privilege contexts like guests and when running outside SGX enclaves. ++ ++The hardware enforces the mitigation for SGX. Likewise, VMMs should ensure ++that guests are not allowed to disable the GDS mitigation. If a host erred and ++allowed this, a guest could theoretically disable GDS mitigation, mount an ++attack, and re-enable it. ++ ++Mitigation mechanism ++-------------------- ++This issue is mitigated in microcode. The microcode defines the following new ++bits: ++ ++ ================================ === ============================ ++ IA32_ARCH_CAPABILITIES[GDS_CTRL] R/O Enumerates GDS vulnerability ++ and mitigation support. ++ IA32_ARCH_CAPABILITIES[GDS_NO] R/O Processor is not vulnerable. ++ IA32_MCU_OPT_CTRL[GDS_MITG_DIS] R/W Disables the mitigation ++ 0 by default. ++ IA32_MCU_OPT_CTRL[GDS_MITG_LOCK] R/W Locks GDS_MITG_DIS=0. Writes ++ to GDS_MITG_DIS are ignored ++ Can't be cleared once set. ++ ================================ === ============================ ++ ++GDS can also be mitigated on systems that don't have updated microcode by ++disabling AVX. This can be done by setting "clearcpuid=avx" on the kernel ++command-line. ++ ++Mitigation control on the kernel command line ++--------------------------------------------- ++The mitigation can be disabled by setting "gather_data_sampling=off" or ++"mitigations=off" on the kernel command line. Not specifying either will ++default to the mitigation being enabled. ++ ++GDS System Information ++------------------------ ++The kernel provides vulnerability status information through sysfs. For ++GDS this can be accessed by the following sysfs file: ++ ++/sys/devices/system/cpu/vulnerabilities/gather_data_sampling ++ ++The possible values contained in this file are: ++ ++ ============================== ============================================= ++ Not affected Processor not vulnerable. ++ Vulnerable Processor vulnerable and mitigation disabled. ++ Vulnerable: No microcode Processor vulnerable and microcode is missing ++ mitigation. ++ Mitigation: Microcode Processor is vulnerable and mitigation is in ++ effect. ++ Mitigation: Microcode (locked) Processor is vulnerable and mitigation is in ++ effect and cannot be disabled. ++ Unknown: Dependent on ++ hypervisor status Running on a virtual guest processor that is ++ affected but with no way to know if host ++ processor is mitigated or vulnerable. ++ ============================== ============================================= ++ ++GDS Default mitigation ++---------------------- ++The updated microcode will enable the mitigation by default. The kernel's ++default action is to leave the mitigation enabled. +--- a/Documentation/admin-guide/hw-vuln/index.rst ++++ b/Documentation/admin-guide/hw-vuln/index.rst +@@ -16,3 +16,4 @@ are configurable at compile, boot or run + multihit.rst + special-register-buffer-data-sampling.rst + processor_mmio_stale_data.rst ++ gather_data_sampling.rst +--- a/Documentation/admin-guide/kernel-parameters.txt ++++ b/Documentation/admin-guide/kernel-parameters.txt +@@ -1290,6 +1290,20 @@ + Format: off | on + default: on + ++ gather_data_sampling= ++ [X86,INTEL] Control the Gather Data Sampling (GDS) ++ mitigation. ++ ++ Gather Data Sampling is a hardware vulnerability which ++ allows unprivileged speculative access to data which was ++ previously stored in vector registers. ++ ++ This issue is mitigated by default in updated microcode. ++ The mitigation may have a performance impact but can be ++ disabled. ++ ++ off: Disable GDS mitigation. ++ + gcov_persist= [GCOV] When non-zero (default), profiling data for + kernel modules is saved and remains accessible via + debugfs, even when the module is unloaded/reloaded. +@@ -2555,22 +2569,23 @@ + Disable all optional CPU mitigations. This + improves system performance, but it may also + expose users to several CPU vulnerabilities. +- Equivalent to: nopti [X86,PPC] ++ Equivalent to: gather_data_sampling=off [X86] + kpti=0 [ARM64] +- nospectre_v1 [PPC] ++ kvm.nx_huge_pages=off [X86] ++ l1tf=off [X86] ++ mds=off [X86] ++ mmio_stale_data=off [X86] ++ no_entry_flush [PPC] ++ no_uaccess_flush [PPC] + nobp=0 [S390] ++ nopti [X86,PPC] ++ nospectre_v1 [PPC] + nospectre_v1 [X86] + nospectre_v2 [X86,PPC,S390,ARM64] +- spectre_v2_user=off [X86] + spec_store_bypass_disable=off [X86,PPC] ++ spectre_v2_user=off [X86] + ssbd=force-off [ARM64] +- l1tf=off [X86] +- mds=off [X86] + tsx_async_abort=off [X86] +- kvm.nx_huge_pages=off [X86] +- no_entry_flush [PPC] +- no_uaccess_flush [PPC] +- mmio_stale_data=off [X86] + + Exceptions: + This does not have any effect on +--- a/arch/x86/include/asm/cpufeatures.h ++++ b/arch/x86/include/asm/cpufeatures.h +@@ -409,5 +409,6 @@ + #define X86_BUG_MMIO_UNKNOWN X86_BUG(26) /* CPU is too old and its MMIO Stale Data status is unknown */ + #define X86_BUG_RETBLEED X86_BUG(27) /* CPU is affected by RETBleed */ + #define X86_BUG_EIBRS_PBRSB X86_BUG(28) /* EIBRS is vulnerable to Post Barrier RSB Predictions */ ++#define X86_BUG_GDS X86_BUG(29) /* CPU is affected by Gather Data Sampling */ + + #endif /* _ASM_X86_CPUFEATURES_H */ +--- a/arch/x86/include/asm/msr-index.h ++++ b/arch/x86/include/asm/msr-index.h +@@ -138,6 +138,15 @@ + * Not susceptible to Post-Barrier + * Return Stack Buffer Predictions. + */ ++#define ARCH_CAP_GDS_CTRL BIT(25) /* ++ * CPU is vulnerable to Gather ++ * Data Sampling (GDS) and ++ * has controls for mitigation. ++ */ ++#define ARCH_CAP_GDS_NO BIT(26) /* ++ * CPU is not vulnerable to Gather ++ * Data Sampling (GDS). ++ */ + + #define MSR_IA32_FLUSH_CMD 0x0000010b + #define L1D_FLUSH BIT(0) /* +@@ -156,6 +165,8 @@ + #define MSR_IA32_MCU_OPT_CTRL 0x00000123 + #define RNGDS_MITG_DIS BIT(0) + #define FB_CLEAR_DIS BIT(3) /* CPU Fill buffer clear disable */ ++#define GDS_MITG_DIS BIT(4) /* Disable GDS mitigation */ ++#define GDS_MITG_LOCKED BIT(5) /* GDS mitigation locked */ + + #define MSR_IA32_SYSENTER_CS 0x00000174 + #define MSR_IA32_SYSENTER_ESP 0x00000175 +--- a/arch/x86/kernel/cpu/bugs.c ++++ b/arch/x86/kernel/cpu/bugs.c +@@ -44,6 +44,7 @@ static void __init md_clear_select_mitig + static void __init taa_select_mitigation(void); + static void __init mmio_select_mitigation(void); + static void __init srbds_select_mitigation(void); ++static void __init gds_select_mitigation(void); + + /* The base value of the SPEC_CTRL MSR without task-specific bits set */ + u64 x86_spec_ctrl_base; +@@ -149,6 +150,7 @@ void __init cpu_select_mitigations(void) + l1tf_select_mitigation(); + md_clear_select_mitigation(); + srbds_select_mitigation(); ++ gds_select_mitigation(); + } + + /* +@@ -600,6 +602,120 @@ static int __init srbds_parse_cmdline(ch + early_param("srbds", srbds_parse_cmdline); + + #undef pr_fmt ++#define pr_fmt(fmt) "GDS: " fmt ++ ++enum gds_mitigations { ++ GDS_MITIGATION_OFF, ++ GDS_MITIGATION_UCODE_NEEDED, ++ GDS_MITIGATION_FULL, ++ GDS_MITIGATION_FULL_LOCKED, ++ GDS_MITIGATION_HYPERVISOR, ++}; ++ ++static enum gds_mitigations gds_mitigation __ro_after_init = GDS_MITIGATION_FULL; ++ ++static const char * const gds_strings[] = { ++ [GDS_MITIGATION_OFF] = "Vulnerable", ++ [GDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode", ++ [GDS_MITIGATION_FULL] = "Mitigation: Microcode", ++ [GDS_MITIGATION_FULL_LOCKED] = "Mitigation: Microcode (locked)", ++ [GDS_MITIGATION_HYPERVISOR] = "Unknown: Dependent on hypervisor status", ++}; ++ ++void update_gds_msr(void) ++{ ++ u64 mcu_ctrl_after; ++ u64 mcu_ctrl; ++ ++ switch (gds_mitigation) { ++ case GDS_MITIGATION_OFF: ++ rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); ++ mcu_ctrl |= GDS_MITG_DIS; ++ break; ++ case GDS_MITIGATION_FULL_LOCKED: ++ /* ++ * The LOCKED state comes from the boot CPU. APs might not have ++ * the same state. Make sure the mitigation is enabled on all ++ * CPUs. ++ */ ++ case GDS_MITIGATION_FULL: ++ rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); ++ mcu_ctrl &= ~GDS_MITG_DIS; ++ break; ++ case GDS_MITIGATION_UCODE_NEEDED: ++ case GDS_MITIGATION_HYPERVISOR: ++ return; ++ }; ++ ++ wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); ++ ++ /* ++ * Check to make sure that the WRMSR value was not ignored. Writes to ++ * GDS_MITG_DIS will be ignored if this processor is locked but the boot ++ * processor was not. ++ */ ++ rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl_after); ++ WARN_ON_ONCE(mcu_ctrl != mcu_ctrl_after); ++} ++ ++static void __init gds_select_mitigation(void) ++{ ++ u64 mcu_ctrl; ++ ++ if (!boot_cpu_has_bug(X86_BUG_GDS)) ++ return; ++ ++ if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) { ++ gds_mitigation = GDS_MITIGATION_HYPERVISOR; ++ goto out; ++ } ++ ++ if (cpu_mitigations_off()) ++ gds_mitigation = GDS_MITIGATION_OFF; ++ /* Will verify below that mitigation _can_ be disabled */ ++ ++ /* No microcode */ ++ if (!(x86_read_arch_cap_msr() & ARCH_CAP_GDS_CTRL)) { ++ gds_mitigation = GDS_MITIGATION_UCODE_NEEDED; ++ goto out; ++ } ++ ++ rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); ++ if (mcu_ctrl & GDS_MITG_LOCKED) { ++ if (gds_mitigation == GDS_MITIGATION_OFF) ++ pr_warn("Mitigation locked. Disable failed.\n"); ++ ++ /* ++ * The mitigation is selected from the boot CPU. All other CPUs ++ * _should_ have the same state. If the boot CPU isn't locked ++ * but others are then update_gds_msr() will WARN() of the state ++ * mismatch. If the boot CPU is locked update_gds_msr() will ++ * ensure the other CPUs have the mitigation enabled. ++ */ ++ gds_mitigation = GDS_MITIGATION_FULL_LOCKED; ++ } ++ ++ update_gds_msr(); ++out: ++ pr_info("%s\n", gds_strings[gds_mitigation]); ++} ++ ++static int __init gds_parse_cmdline(char *str) ++{ ++ if (!str) ++ return -EINVAL; ++ ++ if (!boot_cpu_has_bug(X86_BUG_GDS)) ++ return 0; ++ ++ if (!strcmp(str, "off")) ++ gds_mitigation = GDS_MITIGATION_OFF; ++ ++ return 0; ++} ++early_param("gather_data_sampling", gds_parse_cmdline); ++ ++#undef pr_fmt + #define pr_fmt(fmt) "Spectre V1 : " fmt + + enum spectre_v1_mitigation { +@@ -2147,6 +2263,11 @@ static ssize_t retbleed_show_state(char + return sprintf(buf, "%s\n", retbleed_strings[retbleed_mitigation]); + } + ++static ssize_t gds_show_state(char *buf) ++{ ++ return sysfs_emit(buf, "%s\n", gds_strings[gds_mitigation]); ++} ++ + static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr, + char *buf, unsigned int bug) + { +@@ -2196,6 +2317,9 @@ static ssize_t cpu_show_common(struct de + case X86_BUG_RETBLEED: + return retbleed_show_state(buf); + ++ case X86_BUG_GDS: ++ return gds_show_state(buf); ++ + default: + break; + } +@@ -2260,4 +2384,9 @@ ssize_t cpu_show_retbleed(struct device + { + return cpu_show_common(dev, attr, buf, X86_BUG_RETBLEED); + } ++ ++ssize_t cpu_show_gds(struct device *dev, struct device_attribute *attr, char *buf) ++{ ++ return cpu_show_common(dev, attr, buf, X86_BUG_GDS); ++} + #endif +--- a/arch/x86/kernel/cpu/common.c ++++ b/arch/x86/kernel/cpu/common.c +@@ -1047,6 +1047,8 @@ static const __initconst struct x86_cpu_ + #define MMIO_SBDS BIT(2) + /* CPU is affected by RETbleed, speculating where you would not expect it */ + #define RETBLEED BIT(3) ++/* CPU is affected by GDS */ ++#define GDS BIT(4) + + static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = { + VULNBL_INTEL_STEPPINGS(IVYBRIDGE, X86_STEPPING_ANY, SRBDS), +@@ -1059,18 +1061,20 @@ static const struct x86_cpu_id cpu_vuln_ + VULNBL_INTEL_STEPPINGS(BROADWELL_X, X86_STEPPING_ANY, MMIO), + VULNBL_INTEL_STEPPINGS(BROADWELL_CORE, X86_STEPPING_ANY, SRBDS), + VULNBL_INTEL_STEPPINGS(SKYLAKE_MOBILE, X86_STEPPING_ANY, SRBDS | MMIO | RETBLEED), +- VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPING_ANY, MMIO | RETBLEED), ++ VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPING_ANY, MMIO | RETBLEED | GDS), + VULNBL_INTEL_STEPPINGS(SKYLAKE_DESKTOP, X86_STEPPING_ANY, SRBDS | MMIO | RETBLEED), +- VULNBL_INTEL_STEPPINGS(KABYLAKE_MOBILE, X86_STEPPING_ANY, SRBDS | MMIO | RETBLEED), +- VULNBL_INTEL_STEPPINGS(KABYLAKE_DESKTOP,X86_STEPPING_ANY, SRBDS | MMIO | RETBLEED), ++ VULNBL_INTEL_STEPPINGS(KABYLAKE_MOBILE, X86_STEPPING_ANY, SRBDS | MMIO | RETBLEED | GDS), ++ VULNBL_INTEL_STEPPINGS(KABYLAKE_DESKTOP,X86_STEPPING_ANY, SRBDS | MMIO | RETBLEED | GDS), + VULNBL_INTEL_STEPPINGS(CANNONLAKE_MOBILE,X86_STEPPING_ANY, RETBLEED), +- VULNBL_INTEL_STEPPINGS(ICELAKE_MOBILE, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED), +- VULNBL_INTEL_STEPPINGS(ICELAKE_XEON_D, X86_STEPPING_ANY, MMIO), +- VULNBL_INTEL_STEPPINGS(ICELAKE_X, X86_STEPPING_ANY, MMIO), +- VULNBL_INTEL_STEPPINGS(COMETLAKE, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED), +- VULNBL_INTEL_STEPPINGS(COMETLAKE_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED), ++ VULNBL_INTEL_STEPPINGS(ICELAKE_MOBILE, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS), ++ VULNBL_INTEL_STEPPINGS(ICELAKE_XEON_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_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(LAKEFIELD, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED), +- VULNBL_INTEL_STEPPINGS(ROCKETLAKE, X86_STEPPING_ANY, MMIO | RETBLEED), ++ VULNBL_INTEL_STEPPINGS(ROCKETLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS), + VULNBL_INTEL_STEPPINGS(ATOM_TREMONT, X86_STEPPING_ANY, MMIO | MMIO_SBDS), + VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_X, X86_STEPPING_ANY, MMIO), + VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS), +@@ -1193,6 +1197,16 @@ static void __init cpu_set_bug_bits(stru + !(ia32_cap & ARCH_CAP_PBRSB_NO)) + setup_force_cpu_bug(X86_BUG_EIBRS_PBRSB); + ++ /* ++ * Check if CPU is vulnerable to GDS. If running in a virtual machine on ++ * an affected processor, the VMM may have disabled the use of GATHER by ++ * disabling AVX2. The only way to do this in HW is to clear XCR0[2], ++ * which means that AVX will be disabled. ++ */ ++ if (cpu_matches(cpu_vuln_blacklist, GDS) && !(ia32_cap & ARCH_CAP_GDS_NO) && ++ boot_cpu_has(X86_FEATURE_AVX)) ++ setup_force_cpu_bug(X86_BUG_GDS); ++ + if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN)) + return; + +@@ -1666,6 +1680,8 @@ void identify_secondary_cpu(struct cpuin + validate_apic_and_package_id(c); + x86_spec_ctrl_setup_ap(); + update_srbds_msr(); ++ if (boot_cpu_has_bug(X86_BUG_GDS)) ++ update_gds_msr(); + } + + static __init int setup_noclflush(char *arg) +--- a/arch/x86/kernel/cpu/cpu.h ++++ b/arch/x86/kernel/cpu/cpu.h +@@ -83,6 +83,7 @@ void cpu_select_mitigations(void); + + extern void x86_spec_ctrl_setup_ap(void); + extern void update_srbds_msr(void); ++extern void update_gds_msr(void); + + extern u64 x86_read_arch_cap_msr(void); + +--- a/drivers/base/cpu.c ++++ b/drivers/base/cpu.c +@@ -584,6 +584,12 @@ ssize_t __weak cpu_show_retbleed(struct + return sysfs_emit(buf, "Not affected\n"); + } + ++ssize_t __weak cpu_show_gds(struct device *dev, ++ struct device_attribute *attr, char *buf) ++{ ++ return sysfs_emit(buf, "Not affected\n"); ++} ++ + static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL); + static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL); + static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL); +@@ -595,6 +601,7 @@ static DEVICE_ATTR(itlb_multihit, 0444, + static DEVICE_ATTR(srbds, 0444, cpu_show_srbds, NULL); + static DEVICE_ATTR(mmio_stale_data, 0444, cpu_show_mmio_stale_data, NULL); + static DEVICE_ATTR(retbleed, 0444, cpu_show_retbleed, NULL); ++static DEVICE_ATTR(gather_data_sampling, 0444, cpu_show_gds, NULL); + + static struct attribute *cpu_root_vulnerabilities_attrs[] = { + &dev_attr_meltdown.attr, +@@ -608,6 +615,7 @@ static struct attribute *cpu_root_vulner + &dev_attr_srbds.attr, + &dev_attr_mmio_stale_data.attr, + &dev_attr_retbleed.attr, ++ &dev_attr_gather_data_sampling.attr, + NULL + }; + |