From 181b6f40e9ea80c76756d4d0cdeed396016c487e Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 25 May 2022 18:12:29 +0200 Subject: x86/microcode: Rip out the OLD_INTERFACE Everything should be using the early initrd loading by now. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220525161232.14924-2-bp@alien8.de --- arch/x86/Kconfig | 12 ----- arch/x86/kernel/cpu/microcode/core.c | 100 ----------------------------------- 2 files changed, 112 deletions(-) (limited to 'arch') diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 762a0b6ab8b6..f423a2d87b15 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1350,18 +1350,6 @@ 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)" - 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 - config X86_MSR tristate "/dev/cpu/*/msr - Model-specific register support" help diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 239ff5fcec6a..b72c4134f289 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -373,98 +373,6 @@ 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; @@ -856,10 +764,6 @@ 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 +774,6 @@ 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); -- cgit v1.2.3 From a77a94f86273ce42a39cb479217dd8d68acfe0ff Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 25 May 2022 18:12:30 +0200 Subject: x86/microcode: Default-disable late loading It is dangerous and it should not be used anyway - there's a nice early loading already. Requested-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220525161232.14924-3-bp@alien8.de --- arch/x86/Kconfig | 11 +++++++++++ arch/x86/kernel/cpu/common.c | 2 ++ arch/x86/kernel/cpu/microcode/core.c | 7 ++++++- 3 files changed, 19 insertions(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f423a2d87b15..976309d57a58 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1350,6 +1350,17 @@ config MICROCODE_AMD If you select this option, microcode patch loading support for AMD processors will be enabled. +config MICROCODE_LATE_LOADING + bool "Late microcode loading (DANGEROUS)" + default n + depends on MICROCODE + help + 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" help 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 b72c4134f289..c717db6b6856 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -376,6 +376,7 @@ static int apply_microcode_on_target(int cpu) /* 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? * @@ -543,6 +544,9 @@ put: return ret; } +static DEVICE_ATTR_WO(reload); +#endif + static ssize_t version_show(struct device *dev, struct device_attribute *attr, char *buf) { @@ -559,7 +563,6 @@ 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); @@ -712,7 +715,9 @@ 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 }; -- cgit v1.2.3 From d23d33ea0fcdc4bbb484990bf53867f99c63ccab Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 25 May 2022 18:12:31 +0200 Subject: x86/microcode: Taint and warn on late loading Warn before it is attempted and taint the kernel. Late loading microcode can lead to malfunction of the kernel when the microcode update changes behaviour. There is no way for the kernel to determine whether its safe or not. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220525161232.14924-4-bp@alien8.de --- arch/x86/kernel/cpu/microcode/core.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'arch') diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index c717db6b6856..801b44ac3851 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -493,6 +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); @@ -541,6 +544,8 @@ put: if (ret == 0) ret = size; + add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK); + return ret; } -- cgit v1.2.3 From 0c0fe08c76485fe0178ebb0fa1a2052c727abe94 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 25 May 2022 18:12:32 +0200 Subject: x86/microcode: Remove unnecessary perf callback c93dc84cbe32 ("perf/x86: Add a microcode revision check for SNB-PEBS") checks whether the microcode revision has fixed PEBS issues. This can happen either: 1. At PEBS init time, where the early microcode has been loaded already 2. During late loading, in the microcode_check() callback. So remove the unnecessary call in the microcode loader init routine. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220525161232.14924-5-bp@alien8.de --- arch/x86/kernel/cpu/microcode/core.c | 3 --- 1 file changed, 3 deletions(-) (limited to 'arch') diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 801b44ac3851..ad57e0e4d674 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -756,10 +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(); -- cgit v1.2.3