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author | Linus Torvalds <torvalds@linux-foundation.org> | 2022-06-05 19:55:23 +0200 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-06-05 19:55:23 +0200 |
commit | 9784edd73a08ea08d0ce5606e1f0f729df688c59 (patch) | |
tree | a9247155727c093f98a62af876a476db1a69219f | |
parent | Merge tag 'x86-cleanups-2022-06-05' of git://git.kernel.org/pub/scm/linux/ker... (diff) | |
parent | x86/microcode: Remove unnecessary perf callback (diff) | |
download | linux-9784edd73a08ea08d0ce5606e1f0f729df688c59.tar.xz linux-9784edd73a08ea08d0ce5606e1f0f729df688c59.zip |
Merge tag 'x86-microcode-2022-06-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 microcode updates from Thomas Gleixner:
- Disable late microcode loading by default. Unless the HW people get
their act together and provide a required minimum version in the
microcode header for making a halfways informed decision its just
lottery and broken.
- Warn and taint the kernel when microcode is loaded late
- Remove the old unused microcode loader interface
- Remove a redundant perf callback from the microcode loader
* tag 'x86-microcode-2022-06-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/microcode: Remove unnecessary perf callback
x86/microcode: Taint and warn on late loading
x86/microcode: Default-disable late loading
x86/microcode: Rip out the OLD_INTERFACE
-rw-r--r-- | arch/x86/Kconfig | 15 | ||||
-rw-r--r-- | arch/x86/kernel/cpu/common.c | 2 | ||||
-rw-r--r-- | arch/x86/kernel/cpu/microcode/core.c | 115 |
3 files changed, 20 insertions, 112 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 7df2a9ef3662..9783ebc4e021 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1358,17 +1358,16 @@ config MICROCODE_AMD If you select this option, microcode patch loading support for AMD processors will be enabled. -config MICROCODE_OLD_INTERFACE - bool "Ancient loading interface (DEPRECATED)" +config MICROCODE_LATE_LOADING + bool "Late microcode loading (DANGEROUS)" default n depends on MICROCODE help - DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface - which was used by userspace tools like iucode_tool and microcode.ctl. - It is inadequate because it runs too late to be able to properly - load microcode on a machine and it needs special tools. Instead, you - should've switched to the early loading method with the initrd or - builtin microcode by now: Documentation/x86/microcode.rst + Loading microcode late, when the system is up and executing instructions + is a tricky business and should be avoided if possible. Just the sequence + of synchronizing all cores and SMT threads is one fragile dance which does + not guarantee that cores might not softlock after the loading. Therefore, + use this at your own risk. Late loading taints the kernel too. config X86_MSR tristate "/dev/cpu/*/msr - Model-specific register support" diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 2e9142797c99..c296cb1c0113 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2222,6 +2222,7 @@ void cpu_init_secondary(void) } #endif +#ifdef CONFIG_MICROCODE_LATE_LOADING /* * The microcode loader calls this upon late microcode load to recheck features, * only when microcode has been updated. Caller holds microcode_mutex and CPU @@ -2251,6 +2252,7 @@ void microcode_check(void) pr_warn("x86/CPU: CPU features have changed after loading microcode, but might not take effect.\n"); pr_warn("x86/CPU: Please consider either early loading through initrd/built-in or a potential BIOS update.\n"); } +#endif /* * Invoked from core CPU hotplug code after hotplug operations diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 239ff5fcec6a..ad57e0e4d674 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -373,101 +373,10 @@ static int apply_microcode_on_target(int cpu) return ret; } -#ifdef CONFIG_MICROCODE_OLD_INTERFACE -static int do_microcode_update(const void __user *buf, size_t size) -{ - int error = 0; - int cpu; - - for_each_online_cpu(cpu) { - struct ucode_cpu_info *uci = ucode_cpu_info + cpu; - enum ucode_state ustate; - - if (!uci->valid) - continue; - - ustate = microcode_ops->request_microcode_user(cpu, buf, size); - if (ustate == UCODE_ERROR) { - error = -1; - break; - } else if (ustate == UCODE_NEW) { - apply_microcode_on_target(cpu); - } - } - - return error; -} - -static int microcode_open(struct inode *inode, struct file *file) -{ - return capable(CAP_SYS_RAWIO) ? stream_open(inode, file) : -EPERM; -} - -static ssize_t microcode_write(struct file *file, const char __user *buf, - size_t len, loff_t *ppos) -{ - ssize_t ret = -EINVAL; - unsigned long nr_pages = totalram_pages(); - - if ((len >> PAGE_SHIFT) > nr_pages) { - pr_err("too much data (max %ld pages)\n", nr_pages); - return ret; - } - - cpus_read_lock(); - mutex_lock(µcode_mutex); - - if (do_microcode_update(buf, len) == 0) - ret = (ssize_t)len; - - if (ret > 0) - perf_check_microcode(); - - mutex_unlock(µcode_mutex); - cpus_read_unlock(); - - return ret; -} - -static const struct file_operations microcode_fops = { - .owner = THIS_MODULE, - .write = microcode_write, - .open = microcode_open, - .llseek = no_llseek, -}; - -static struct miscdevice microcode_dev = { - .minor = MICROCODE_MINOR, - .name = "microcode", - .nodename = "cpu/microcode", - .fops = µcode_fops, -}; - -static int __init microcode_dev_init(void) -{ - int error; - - error = misc_register(µcode_dev); - if (error) { - pr_err("can't misc_register on minor=%d\n", MICROCODE_MINOR); - return error; - } - - return 0; -} - -static void __exit microcode_dev_exit(void) -{ - misc_deregister(µcode_dev); -} -#else -#define microcode_dev_init() 0 -#define microcode_dev_exit() do { } while (0) -#endif - /* fake device for request_firmware */ static struct platform_device *microcode_pdev; +#ifdef CONFIG_MICROCODE_LATE_LOADING /* * Late loading dance. Why the heavy-handed stomp_machine effort? * @@ -584,6 +493,9 @@ static int microcode_reload_late(void) { int ret; + pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n"); + pr_err("You should switch to early loading, if possible.\n"); + atomic_set(&late_cpus_in, 0); atomic_set(&late_cpus_out, 0); @@ -632,9 +544,14 @@ put: if (ret == 0) ret = size; + add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK); + return ret; } +static DEVICE_ATTR_WO(reload); +#endif + static ssize_t version_show(struct device *dev, struct device_attribute *attr, char *buf) { @@ -651,7 +568,6 @@ static ssize_t pf_show(struct device *dev, return sprintf(buf, "0x%x\n", uci->cpu_sig.pf); } -static DEVICE_ATTR_WO(reload); static DEVICE_ATTR(version, 0444, version_show, NULL); static DEVICE_ATTR(processor_flags, 0444, pf_show, NULL); @@ -804,7 +720,9 @@ static int mc_cpu_down_prep(unsigned int cpu) } static struct attribute *cpu_root_microcode_attrs[] = { +#ifdef CONFIG_MICROCODE_LATE_LOADING &dev_attr_reload.attr, +#endif NULL }; @@ -838,10 +756,7 @@ static int __init microcode_init(void) cpus_read_lock(); mutex_lock(µcode_mutex); - error = subsys_interface_register(&mc_cpu_interface); - if (!error) - perf_check_microcode(); mutex_unlock(µcode_mutex); cpus_read_unlock(); @@ -856,10 +771,6 @@ static int __init microcode_init(void) goto out_driver; } - error = microcode_dev_init(); - if (error) - goto out_ucode_group; - register_syscore_ops(&mc_syscore_ops); cpuhp_setup_state_nocalls(CPUHP_AP_MICROCODE_LOADER, "x86/microcode:starting", mc_cpu_starting, NULL); @@ -870,10 +781,6 @@ static int __init microcode_init(void) return 0; - out_ucode_group: - sysfs_remove_group(&cpu_subsys.dev_root->kobj, - &cpu_root_microcode_group); - out_driver: cpus_read_lock(); mutex_lock(µcode_mutex); |