4.14-stable review patch. If anyone has any objections, please let me know.
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From: Greg Kroah-Hartman gregkh@linuxfoundation.org
This reverts commit 8a13906ae519b3ed95cd0fb73f1098b46362f6c4 which is commit 53c613fe6349994f023245519265999eed75957f upstream.
It's not ready for the stable trees as there are major slowdowns involved with this patch.
Reported-by: Jiri Kosina jkosina@suse.cz Cc: Thomas Gleixner tglx@linutronix.de Cc: Peter Zijlstra peterz@infradead.org Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: "WoodhouseDavid" dwmw@amazon.co.uk Cc: Andi Kleen ak@linux.intel.com Cc: Tim Chen tim.c.chen@linux.intel.com Cc: "SchauflerCasey" casey.schaufler@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/cpu/bugs.c | 57 ++++----------------------------------------- kernel/cpu.c | 11 -------- 2 files changed, 7 insertions(+), 61 deletions(-)
--- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -34,10 +34,12 @@ static void __init spectre_v2_select_mit static void __init ssb_select_mitigation(void); static void __init l1tf_select_mitigation(void);
-/* The base value of the SPEC_CTRL MSR that always has to be preserved. */ -u64 x86_spec_ctrl_base; +/* + * Our boot-time value of the SPEC_CTRL MSR. We read it once so that any + * writes to SPEC_CTRL contain whatever reserved bits have been set. + */ +u64 __ro_after_init x86_spec_ctrl_base; EXPORT_SYMBOL_GPL(x86_spec_ctrl_base); -static DEFINE_MUTEX(spec_ctrl_mutex);
/* * The vendor and possibly platform specific bits which can be modified in @@ -321,46 +323,6 @@ static enum spectre_v2_mitigation_cmd __ return cmd; }
-static bool stibp_needed(void) -{ - if (spectre_v2_enabled == SPECTRE_V2_NONE) - return false; - - if (!boot_cpu_has(X86_FEATURE_STIBP)) - return false; - - return true; -} - -static void update_stibp_msr(void *info) -{ - wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); -} - -void arch_smt_update(void) -{ - u64 mask; - - if (!stibp_needed()) - return; - - mutex_lock(&spec_ctrl_mutex); - mask = x86_spec_ctrl_base; - if (cpu_smt_control == CPU_SMT_ENABLED) - mask |= SPEC_CTRL_STIBP; - else - mask &= ~SPEC_CTRL_STIBP; - - if (mask != x86_spec_ctrl_base) { - pr_info("Spectre v2 cross-process SMT mitigation: %s STIBP\n", - cpu_smt_control == CPU_SMT_ENABLED ? - "Enabling" : "Disabling"); - x86_spec_ctrl_base = mask; - on_each_cpu(update_stibp_msr, NULL, 1); - } - mutex_unlock(&spec_ctrl_mutex); -} - static void __init spectre_v2_select_mitigation(void) { enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline(); @@ -460,9 +422,6 @@ specv2_set_mode: setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW); pr_info("Enabling Restricted Speculation for firmware calls\n"); } - - /* Enable STIBP if appropriate */ - arch_smt_update(); }
#undef pr_fmt @@ -855,8 +814,6 @@ static ssize_t l1tf_show_state(char *buf static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr, char *buf, unsigned int bug) { - int ret; - if (!boot_cpu_has_bug(bug)) return sprintf(buf, "Not affected\n");
@@ -871,12 +828,10 @@ static ssize_t cpu_show_common(struct de return sprintf(buf, "Mitigation: __user pointer sanitization\n");
case X86_BUG_SPECTRE_V2: - ret = sprintf(buf, "%s%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled], + return sprintf(buf, "%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled], boot_cpu_has(X86_FEATURE_USE_IBPB) ? ", IBPB" : "", boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "", - (x86_spec_ctrl_base & SPEC_CTRL_STIBP) ? ", STIBP" : "", spectre_v2_module_string()); - return ret;
case X86_BUG_SPEC_STORE_BYPASS: return sprintf(buf, "%s\n", ssb_strings[ssb_mode]); --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2045,12 +2045,6 @@ static void cpuhp_online_cpu_device(unsi kobject_uevent(&dev->kobj, KOBJ_ONLINE); }
-/* - * Architectures that need SMT-specific errata handling during SMT hotplug - * should override this. - */ -void __weak arch_smt_update(void) { }; - static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) { int cpu, ret = 0; @@ -2077,10 +2071,8 @@ static int cpuhp_smt_disable(enum cpuhp_ */ cpuhp_offline_cpu_device(cpu); } - if (!ret) { + if (!ret) cpu_smt_control = ctrlval; - arch_smt_update(); - } cpu_maps_update_done(); return ret; } @@ -2091,7 +2083,6 @@ static int cpuhp_smt_enable(void)
cpu_maps_update_begin(); cpu_smt_control = CPU_SMT_ENABLED; - arch_smt_update(); for_each_present_cpu(cpu) { /* Skip online CPUs and CPUs on offline nodes */ if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))