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Date: Tue, 27 Jun 2017 19:06:30 -0500 From: Jack Miller <jack@...ezen.org> To: linux-kernel@...r.kernel.org Cc: tglx@...utronix.de, bp@...e.de, Yazen.Ghannam@....com, x86@...nel.org Subject: [PATCH] x86/mce/AMD: Fix partial SMCA bank init when CPU 0 != thread 0 After a call to firmware SwitchBSP(), Linux can be booted with a thread that isn't the first in the system. That thread automatically becomes CPU 0. Currently get_smca_bank_info() queries CPU 0's MCA types, but if CPU 0 != hardware thread 0, it will get an incomplete list of MCA types in smca_banks. This causes get_name() to return NULL when initing hardware thread 0's additional types, and then the following error when creating the bank kobj in threshold_create_bank(): [ 1.171552] kobject: can not set name properly! [ 1.171569] kobject_create_and_add: kobject_add error: -12 This error path isn't correctly handled. threshold_init_device() fails, but later if a thread is offlined, threshold_remove_bank() causes a BUG: [ 67.491772] BUG: unable to handle kernel NULL pointer dereference at (null) [ 67.491781] IP: mce_threshold_remove_device.part.7+0x82/0x2c0 because per_cpu(threshold_banks, cpu) is unexpectedly NULL. This patch fixes get_smca_bank_info() to query hardware thread 0, not necessarily CPU 0, to get a full set of MCA types. I'm uncertain that reading the APIC ID is correct here, and this will fail if there is AMD hardware where hardware thread 0's APIC ID != 0, but the other topology/CPUID based functions don't seem to easily differentiate CPU 0 and thread 0 or possibly aren't inited at this point. Suggestions for a better mechanism welcome. Signed-off-by: Jack Miller <jack@...ezen.org> --- arch/x86/kernel/cpu/mcheck/mce_amd.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c index 6e4a047e4b68..9d74adcf34d2 100644 --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c @@ -170,8 +170,8 @@ static void get_smca_bank_info(unsigned int bank) struct smca_hwid *s_hwid; u32 high, instance_id; - /* Collect bank_info using CPU 0 for now. */ - if (cpu) + /* Collect bank_info using hardware thread 0 for now. */ + if (apic->get_apic_id(apic->read(APIC_ID)) != 0) return; if (rdmsr_safe_on_cpu(cpu, MSR_AMD64_SMCA_MCx_IPID(bank), &instance_id, &high)) { -- 2.13.2
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