From: Yazen Ghannam <[email protected]> The OS is expected to write all bits to MCA_CTL for each bank, thus enabling error reporting in all banks. However, some banks may be unused in which case the registers for such banks are Read-as-Zero/Writes-Ignored. Also, the OS may avoid setting some control bits because of quirks, etc.
A bank can be considered uninitialized if the MCA_CTL register returns zero. This is because either the OS did not write anything or because the hardware is enforcing RAZ/WI for the bank. Set a bank's init value based on if the control bits are set or not in hardware. Return an error code in the sysfs interface for uninitialized banks. Do a final bank init check in a separate function which is not part of any user-controlled code flows. This is so a user may enable/disable a bank during runtime without having to restart their system. [ bp: Massage a bit. Discover bank init state at boot. ] Signed-off-by: Yazen Ghannam <[email protected]> --- Link: https://lkml.kernel.org/r/[email protected] v3->v4: * Patch 5 version 3 was zapped. * This is based on new patch from Boris which was based on Patch 6 version 3. * Reworked new patch to fix sysfs issue with disabled banks. v2->v3: * No change. v1->v2: * No change. arch/x86/kernel/cpu/mce/core.c | 39 ++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c index 6813712d8648..ae7723a942f6 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -1490,6 +1490,11 @@ static void __mcheck_cpu_mce_banks_init(void) for (i = 0; i < n_banks; i++) { struct mce_bank *b = &mce_banks[i]; + /* + * Init them all, __mcheck_cpu_apply_quirks() is going to apply + * the required vendor quirks before + * __mcheck_cpu_init_clear_banks() does the final bank setup. + */ b->ctl = -1ULL; b->init = 1; } @@ -1562,6 +1567,33 @@ static void __mcheck_cpu_init_clear_banks(void) } } +/* + * Do a final check to see if there are any unused/RAZ banks. + * + * This must be done after the banks have been initialized and any quirks have + * been applied. + * + * Do not call this from any user-initialed flows, e.g. CPU hotplug or sysfs. + * Otherwise, a user who disables a bank will not be able to re-enable it + * without a system reboot. + */ +static void __mcheck_cpu_check_banks(void) +{ + struct mce_bank *mce_banks = this_cpu_ptr(mce_banks_array); + u64 msrval; + int i; + + for (i = 0; i < this_cpu_read(mce_num_banks); i++) { + struct mce_bank *b = &mce_banks[i]; + + if (!b->init) + continue; + + rdmsrl(msr_ops.ctl(i), msrval); + b->init = !!msrval; + } +} + /* * During IFU recovery Sandy Bridge -EP4S processors set the RIPV and * EIPV bits in MCG_STATUS to zero on the affected logical processor (SDM @@ -1849,6 +1881,7 @@ void mcheck_cpu_init(struct cpuinfo_x86 *c) __mcheck_cpu_init_generic(); __mcheck_cpu_init_vendor(c); __mcheck_cpu_init_clear_banks(); + __mcheck_cpu_check_banks(); __mcheck_cpu_setup_timer(); } @@ -2085,6 +2118,9 @@ static ssize_t show_bank(struct device *s, struct device_attribute *attr, b = &per_cpu(mce_banks_array, s->id)[bank]; + if (!b->init) + return -ENODEV; + return sprintf(buf, "%llx\n", b->ctl); } @@ -2103,6 +2139,9 @@ static ssize_t set_bank(struct device *s, struct device_attribute *attr, b = &per_cpu(mce_banks_array, s->id)[bank]; + if (!b->init) + return -ENODEV; + b->ctl = new; mce_restart(); -- 2.17.1
