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SubjectRe: [PATCH v2 2/6] x86/MCE: Handle MCA controls in a per_cpu way
On Thu, Apr 11, 2019 at 08:18:01PM +0000, Ghannam, Yazen wrote:
> arch/x86/kernel/cpu/mce/core.c | 77 ++++++++++++++++++++++------------
> 1 file changed, 51 insertions(+), 26 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 8d0d1e8425db..aa41f41e5931 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -64,16 +64,21 @@ static DEFINE_MUTEX(mce_sysfs_mutex);
>
> DEFINE_PER_CPU(unsigned, mce_exception_count);
>
> +struct mce_bank {
> + u64 ctl; /* subevents to enable */
> + bool init; /* initialise bank? */
> +};

Pls keep original members alignment.

> +static DEFINE_PER_CPU_READ_MOSTLY(struct mce_bank *, mce_banks);
> +
> #define ATTR_LEN 16
> /* One object for each MCE bank, shared by all CPUs */
> -struct mce_bank {
> - u64 ctl; /* subevents to enable */
> - bool init; /* initialise bank? */
> +struct mce_bank_dev {
> struct device_attribute attr; /* device attribute */
> char attrname[ATTR_LEN]; /* attribute name */
> + u8 bank; /* bank number */
> };
> +static struct mce_bank_dev mce_bank_devs[MAX_NR_BANKS];
>
> -static struct mce_bank *mce_banks __read_mostly;
> struct mce_vendor_flags mce_flags __read_mostly;
>
> struct mca_config mca_cfg __read_mostly = {
> @@ -695,7 +700,7 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
> m.tsc = rdtsc();
>
> for (i = 0; i < mca_cfg.banks; i++) {
> - if (!mce_banks[i].ctl || !test_bit(i, *b))
> + if (!this_cpu_read(mce_banks)[i].ctl || !test_bit(i, *b))
> continue;
>
> m.misc = 0;
> @@ -1138,7 +1143,7 @@ static void __mc_scan_banks(struct mce *m, struct mce *final,
> if (!test_bit(i, valid_banks))
> continue;
>
> - if (!mce_banks[i].ctl)
> + if (!this_cpu_read(mce_banks)[i].ctl)
> continue;
>
> m->misc = 0;
> @@ -1475,16 +1480,19 @@ static int __mcheck_cpu_mce_banks_init(void)
> {
> int i;
>
> - mce_banks = kcalloc(MAX_NR_BANKS, sizeof(struct mce_bank), GFP_KERNEL);
> - if (!mce_banks)
> + per_cpu(mce_banks, smp_processor_id()) =
> + kcalloc(MAX_NR_BANKS, sizeof(struct mce_bank), GFP_KERNEL);
> +
> + if (!this_cpu_read(mce_banks))
> return -ENOMEM;
>
> for (i = 0; i < MAX_NR_BANKS; i++) {
> - struct mce_bank *b = &mce_banks[i];
> + struct mce_bank *b = &this_cpu_read(mce_banks)[i];
>
> b->ctl = -1ULL;
> b->init = 1;
> }
> +
> return 0;
> }

Instead of doing all those per-CPU accesses in the function, you can use
a local pointer and assign it once in the end, before returning.

Also, fix the similar situation where you have multiple per-CPU accesses
in a single function - assign to a local pointer instead and do all the
accesses through it.

> @@ -1504,7 +1512,7 @@ static int __mcheck_cpu_cap_init(void)
>
> mca_cfg.banks = max(mca_cfg.banks, b);
>
> - if (!mce_banks) {
> + if (!this_cpu_read(mce_banks)) {
> int err = __mcheck_cpu_mce_banks_init();
> if (err)
> return err;
> @@ -1547,7 +1555,7 @@ static void __mcheck_cpu_init_clear_banks(void)
> int i;
>
> for (i = 0; i < mca_cfg.banks; i++) {
> - struct mce_bank *b = &mce_banks[i];
> + struct mce_bank *b = &this_cpu_read(mce_banks)[i];
>
> if (!b->init)
> continue;
> @@ -1602,7 +1610,7 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)
> * trips off incorrectly with the IOMMU & 3ware
> * & Cerberus:
> */
> - clear_bit(10, (unsigned long *)&mce_banks[4].ctl);
> + clear_bit(10, (unsigned long *)&this_cpu_read(mce_banks)[4].ctl);
> }
> if (c->x86 < 0x11 && cfg->bootlog < 0) {
> /*
> @@ -1616,7 +1624,7 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)
> * by default.
> */
> if (c->x86 == 6 && cfg->banks > 0)
> - mce_banks[0].ctl = 0;
> + this_cpu_read(mce_banks)[0].ctl = 0;
>
> /*
> * overflow_recov is supported for F15h Models 00h-0fh
> @@ -1638,7 +1646,7 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)
> */
>
> if (c->x86 == 6 && c->x86_model < 0x1A && cfg->banks > 0)
> - mce_banks[0].init = 0;
> + this_cpu_read(mce_banks)[0].init = 0;
>
> /*
> * All newer Intel systems support MCE broadcasting. Enable
> @@ -1952,7 +1960,7 @@ static void mce_disable_error_reporting(void)
> int i;
>
> for (i = 0; i < mca_cfg.banks; i++) {
> - struct mce_bank *b = &mce_banks[i];
> + struct mce_bank *b = &this_cpu_read(mce_banks)[i];
>
> if (b->init)
> wrmsrl(msr_ops.ctl(i), 0);
> @@ -2051,26 +2059,41 @@ static struct bus_type mce_subsys = {
>
> DEFINE_PER_CPU(struct device *, mce_device);
>
> -static inline struct mce_bank *attr_to_bank(struct device_attribute *attr)
> +static inline struct mce_bank_dev *attr_to_bank(struct device_attribute *attr)
> {
> - return container_of(attr, struct mce_bank, attr);
> + return container_of(attr, struct mce_bank_dev, attr);
> }
>
> static ssize_t show_bank(struct device *s, struct device_attribute *attr,
> char *buf)
> {
> - return sprintf(buf, "%llx\n", attr_to_bank(attr)->ctl);
> + struct mce_bank *b;
> + u8 bank = attr_to_bank(attr)->bank;

Please sort function local variables declaration in a reverse christmas
tree order:

<type A> longest_variable_name;
<type B> shorter_var_name;
<type C> even_shorter;
<type D> i;

> +
> + if (bank >= mca_cfg.banks)
> + return -EINVAL;
> +
> + b = &per_cpu(mce_banks, s->id)[bank];
> +
> + return sprintf(buf, "%llx\n", b->ctl);
> }
>
> static ssize_t set_bank(struct device *s, struct device_attribute *attr,
> const char *buf, size_t size)
> {
> u64 new;
> + struct mce_bank *b;
> + u8 bank = attr_to_bank(attr)->bank;

Ditto.

> if (kstrtou64(buf, 0, &new) < 0)
> return -EINVAL;
>
> - attr_to_bank(attr)->ctl = new;
> + if (bank >= mca_cfg.banks)
> + return -EINVAL;
> +
> + b = &per_cpu(mce_banks, s->id)[bank];
> +
> + b->ctl = new;
> mce_restart();
>
> return size;
> @@ -2185,7 +2208,7 @@ static void mce_device_release(struct device *dev)
> kfree(dev);
> }
>
> -/* Per cpu device init. All of the cpus still share the same ctrl bank: */
> +/* Per cpu device init. All of the cpus still share the same bank device: */

s/cpu/CPU/g, while at it.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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