From c9fc3f778a6a215ace14ee556067c73982b6d40f Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Thu, 21 Jun 2012 14:07:16 +0200 Subject: x86, microcode: Sanitize per-cpu microcode reloading interface Microcode reloading in a per-core manner is a very bad idea for both major x86 vendors. And the thing is, we have such interface with which we can end up with different microcode versions applied on different cores of an otherwise homogeneous wrt (family,model,stepping) system. So turn off the possibility of doing that per core and allow it only system-wide. This is a minimal fix which we'd like to see in stable too thus the more-or-less arbitrary decision to allow system-wide reloading only on the BSP: $ echo 1 > /sys/devices/system/cpu/cpu0/microcode/reload ... and disable the interface on the other cores: $ echo 1 > /sys/devices/system/cpu/cpu23/microcode/reload -bash: echo: write error: Invalid argument Also, allowing the reload only from one CPU (the BSP in that case) doesn't allow the reload procedure to degenerate into an O(n^2) deal when triggering reloads from all /sys/devices/system/cpu/cpuX/microcode/reload sysfs nodes simultaneously. A more generic fix will follow. Cc: Henrique de Moraes Holschuh Cc: Peter Zijlstra Signed-off-by: Borislav Petkov Link: http://lkml.kernel.org/r/1340280437-7718-2-git-send-email-bp@amd64.org Signed-off-by: H. Peter Anvin Cc: --- arch/x86/kernel/microcode_core.c | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c index fbdfc691718..24b852b61be 100644 --- a/arch/x86/kernel/microcode_core.c +++ b/arch/x86/kernel/microcode_core.c @@ -298,19 +298,31 @@ static ssize_t reload_store(struct device *dev, const char *buf, size_t size) { unsigned long val; - int cpu = dev->id; - ssize_t ret = 0; + int cpu; + ssize_t ret = 0, tmp_ret; + + /* allow reload only from the BSP */ + if (boot_cpu_data.cpu_index != dev->id) + return -EINVAL; ret = kstrtoul(buf, 0, &val); if (ret) return ret; - if (val == 1) { - get_online_cpus(); - if (cpu_online(cpu)) - ret = reload_for_cpu(cpu); - put_online_cpus(); + if (val != 1) + return size; + + get_online_cpus(); + for_each_online_cpu(cpu) { + tmp_ret = reload_for_cpu(cpu); + if (tmp_ret != 0) + pr_warn("Error reloading microcode on CPU %d\n", cpu); + + /* save retval of the first encountered reload error */ + if (!ret) + ret = tmp_ret; } + put_online_cpus(); if (!ret) ret = size; -- cgit v1.2.3 From 3d8986bc7f309483ee09c7a02888bab09072c19b Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Thu, 21 Jun 2012 14:07:17 +0200 Subject: x86, microcode: Make reload interface per system The reload interface should be per-system so that a full system ucode reload happens (on each core) when doing echo 1 > /sys/devices/system/cpu/microcode/reload Move it to the cpu subsys directory instead of it being per-cpu. Cc: Henrique de Moraes Holschuh Cc: Peter Zijlstra Signed-off-by: Borislav Petkov Link: http://lkml.kernel.org/r/1340280437-7718-3-git-send-email-bp@amd64.org Signed-off-by: H. Peter Anvin --- arch/x86/kernel/microcode_core.c | 36 ++++++++++++++++++++++++++++-------- 1 file changed, 28 insertions(+), 8 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c index 24b852b61be..947e4c64b1d 100644 --- a/arch/x86/kernel/microcode_core.c +++ b/arch/x86/kernel/microcode_core.c @@ -301,10 +301,6 @@ static ssize_t reload_store(struct device *dev, int cpu; ssize_t ret = 0, tmp_ret; - /* allow reload only from the BSP */ - if (boot_cpu_data.cpu_index != dev->id) - return -EINVAL; - ret = kstrtoul(buf, 0, &val); if (ret) return ret; @@ -351,7 +347,6 @@ static DEVICE_ATTR(version, 0400, version_show, NULL); static DEVICE_ATTR(processor_flags, 0400, pf_show, NULL); static struct attribute *mc_default_attrs[] = { - &dev_attr_reload.attr, &dev_attr_version.attr, &dev_attr_processor_flags.attr, NULL @@ -528,6 +523,16 @@ static const struct x86_cpu_id microcode_id[] = { MODULE_DEVICE_TABLE(x86cpu, microcode_id); #endif +static struct attribute *cpu_root_microcode_attrs[] = { + &dev_attr_reload.attr, + NULL +}; + +static struct attribute_group cpu_root_microcode_group = { + .name = "microcode", + .attrs = cpu_root_microcode_attrs, +}; + static int __init microcode_init(void) { struct cpuinfo_x86 *c = &cpu_data(0); @@ -559,9 +564,17 @@ static int __init microcode_init(void) if (error) goto out_pdev; + error = sysfs_create_group(&cpu_subsys.dev_root->kobj, + &cpu_root_microcode_group); + + if (error) { + pr_err("Error creating microcode group!\n"); + goto out_driver; + } + error = microcode_dev_init(); if (error) - goto out_driver; + goto out_ucode_group; register_syscore_ops(&mc_syscore_ops); register_hotcpu_notifier(&mc_cpu_notifier); @@ -571,7 +584,11 @@ static int __init microcode_init(void) return 0; -out_driver: + out_ucode_group: + sysfs_remove_group(&cpu_subsys.dev_root->kobj, + &cpu_root_microcode_group); + + out_driver: get_online_cpus(); mutex_lock(µcode_mutex); @@ -580,7 +597,7 @@ out_driver: mutex_unlock(µcode_mutex); put_online_cpus(); -out_pdev: + out_pdev: platform_device_unregister(microcode_pdev); return error; @@ -596,6 +613,9 @@ static void __exit microcode_exit(void) unregister_hotcpu_notifier(&mc_cpu_notifier); unregister_syscore_ops(&mc_syscore_ops); + sysfs_remove_group(&cpu_subsys.dev_root->kobj, + &cpu_root_microcode_group); + get_online_cpus(); mutex_lock(µcode_mutex); -- cgit v1.2.3