diff options
Diffstat (limited to 'debian/patches/bugfix/x86/gds/x86-speculation-add-gather-data-sampling-mitigation.patch')
| -rw-r--r-- | debian/patches/bugfix/x86/gds/x86-speculation-add-gather-data-sampling-mitigation.patch | 562 |
1 files changed, 0 insertions, 562 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 deleted file mode 100644 index c426811c6..000000000 --- a/debian/patches/bugfix/x86/gds/x86-speculation-add-gather-data-sampling-mitigation.patch +++ /dev/null @@ -1,562 +0,0 @@ -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 - }; - |