Messages in this thread Patch in this message | | | From | Ashok Raj <> | Subject | [v2 04/13] x86/microcode: Fix microcode_check() compare after a new uCode update | Date | Thu, 3 Nov 2022 17:58:52 +0000 |
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microcode_check() seems to take a snapshot after an update to compare with previously cached values of x86_capabilities. Some capabilities can be turned off by OS as a result of certain command line parameters or due to some configuration.
Even though there was no change in CPUID bits, reloading the same microcode threw a warning, that some CPUID bits changed.
To eliminate the false warning, take a snapshot before the update and one after the update. This eliminates the miscompare.
Also move the microcode_check() from cpu/common.c -> cpu/microcode/core.c
Reviewed-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Ashok Raj <ashok.raj@intel.com> --- arch/x86/include/asm/processor.h | 1 - arch/x86/kernel/cpu/common.c | 32 ----------------- arch/x86/kernel/cpu/microcode/core.c | 51 +++++++++++++++++++++++++++- 3 files changed, 50 insertions(+), 34 deletions(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 67c9d73b31fa..2acc8ae0bf47 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -835,7 +835,6 @@ bool xen_set_default_idle(void); #endif void __noreturn stop_this_cpu(void *dummy); -void microcode_check(void); enum l1tf_mitigations { L1TF_MITIGATION_OFF, diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 3e508f239098..bbd362ead043 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2305,38 +2305,6 @@ 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 - * hotplug lock. - */ -void microcode_check(void) -{ - struct cpuinfo_x86 info; - - perf_check_microcode(); - - /* Reload CPUID max function as it might've changed. */ - info.cpuid_level = cpuid_eax(0); - - /* - * Copy all capability leafs to pick up the synthetic ones so that - * memcmp() below doesn't fail on that. The ones coming from CPUID will - * get overwritten in get_cpu_cap(). - */ - memcpy(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability)); - - get_cpu_cap(&info); - - if (!memcmp(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability))) - return; - - 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 712aafff96e0..9ed1f6e138d6 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -40,6 +40,8 @@ #include <asm/cmdline.h> #include <asm/setup.h> +#include "../cpu.h" + #define DRIVER_VERSION "2.2" static struct microcode_ops *microcode_ops; @@ -431,6 +433,51 @@ static int __reload_late(void *info) return ret; } +static void copy_cpu_caps(struct cpuinfo_x86 *info) +{ + /* Reload CPUID max function as it might've changed. */ + info->cpuid_level = cpuid_eax(0); + + /* + * Copy all capability leafs to pick up the synthetic ones so that + * memcmp() below doesn't fail on that. The ones coming from CPUID will + * get overwritten in get_cpu_cap(). + */ + memcpy(info->x86_capability, &boot_cpu_data.x86_capability, sizeof(info->x86_capability)); + + get_cpu_cap(info); +} + +/* + * The microcode loader calls this upon late microcode load to recheck features, + * only when microcode has been updated. Caller holds microcode_mutex and CPU + * hotplug lock. + */ +static void microcode_check(struct cpuinfo_x86 *orig) +{ + struct cpuinfo_x86 info; + + perf_check_microcode(); + + /* Reload CPUID max function as it might've changed. */ + info.cpuid_level = cpuid_eax(0); + + /* + * Copy all capability leafs to pick up the synthetic ones so that + * memcmp() below doesn't fail on that. The ones coming from CPUID will + * get overwritten in get_cpu_cap(). + */ + memcpy(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability)); + + get_cpu_cap(&info); + + if (!memcmp(info.x86_capability, &orig->x86_capability, sizeof(info.x86_capability))) + return; + + 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"); +} + /* * Reload microcode late on all CPUs. Wait for a sec until they * all gather together. @@ -438,6 +485,7 @@ static int __reload_late(void *info) static int microcode_reload_late(void) { int old = boot_cpu_data.microcode, ret; + struct cpuinfo_x86 info; 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"); @@ -445,9 +493,10 @@ static int microcode_reload_late(void) atomic_set(&late_cpus_in, 0); atomic_set(&late_cpus_out, 0); + copy_cpu_caps(&info); ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask); if (ret == 0) - microcode_check(); + microcode_check(&info); pr_info("Reload completed, microcode revision: 0x%x -> 0x%x\n", old, boot_cpu_data.microcode); -- 2.34.1
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