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Subject[PATCH 4/5] x86/MCE: Make number of MCA banks per_cpu
Date
From: Yazen Ghannam <yazen.ghannam@amd.com>

The number of MCA banks is provided per logical CPU. Historically, this
number has been the same across all CPUs, but this is not an
architectural guarantee. Future AMD systems may have MCA bank counts
that vary between logical CPUs in a system.

This issue was partially addressed in

commit ("006c077041dc x86/mce: Handle varying MCA bank counts")

by allocating structures using the maximum number of MCA banks and by
saving the maximum MCA bank count in a system as the global count. This
means that some extra structures are allocated. Also, this means that
CPUs will spend more time in the #MC and other handlers checking extra
MCA banks.

Define the number of MCA banks as a per_cpu variable. Replace all uses
of mca_cfg.banks with this.

Also, use the per_cpu bank count when allocating per_cpu structures.

Print the number of banks per CPU as a debug message for those who may
be interested.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
---
arch/x86/kernel/cpu/mce/amd.c | 16 +++++-----
arch/x86/kernel/cpu/mce/core.c | 49 +++++++++++++++++-------------
arch/x86/kernel/cpu/mce/inject.c | 7 +----
arch/x86/kernel/cpu/mce/internal.h | 2 +-
4 files changed, 38 insertions(+), 36 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index f0644b59848d..acce672efb45 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -493,7 +493,7 @@ static u32 get_block_address(u32 current_addr, u32 low, u32 high,
{
u32 addr = 0, offset = 0;

- if ((bank >= mca_cfg.banks) || (block >= NR_BLOCKS))
+ if ((bank >= per_cpu(num_banks, cpu)) || (block >= NR_BLOCKS))
return addr;

if (mce_flags.smca)
@@ -605,7 +605,7 @@ void mce_amd_feature_init(struct cpuinfo_x86 *c)

disable_err_thresholding(c);

- for (bank = 0; bank < mca_cfg.banks; ++bank) {
+ for (bank = 0; bank < this_cpu_read(num_banks); ++bank) {
if (mce_flags.smca)
smca_configure(bank, cpu);

@@ -948,7 +948,7 @@ static void amd_deferred_error_interrupt(void)
{
unsigned int bank;

- for (bank = 0; bank < mca_cfg.banks; ++bank)
+ for (bank = 0; bank < this_cpu_read(num_banks); ++bank)
log_error_deferred(bank);
}

@@ -989,7 +989,7 @@ static void amd_threshold_interrupt(void)
struct threshold_block *first_block = NULL, *block = NULL, *tmp = NULL;
unsigned int bank, cpu = smp_processor_id();

- for (bank = 0; bank < mca_cfg.banks; ++bank) {
+ for (bank = 0; bank < this_cpu_read(num_banks); ++bank) {
if (!(per_cpu(bank_map, cpu) & (1 << bank)))
continue;

@@ -1176,7 +1176,7 @@ static int allocate_threshold_blocks(unsigned int cpu, unsigned int bank,
u32 low, high;
int err;

- if ((bank >= mca_cfg.banks) || (block >= NR_BLOCKS))
+ if ((bank >= per_cpu(num_banks, cpu)) || (block >= NR_BLOCKS))
return 0;

if (rdmsr_safe_on_cpu(cpu, address, &low, &high))
@@ -1410,7 +1410,7 @@ int mce_threshold_remove_device(unsigned int cpu)
{
unsigned int bank;

- for (bank = 0; bank < mca_cfg.banks; ++bank) {
+ for (bank = 0; bank < per_cpu(num_banks, cpu); ++bank) {
if (!(per_cpu(bank_map, cpu) & (1 << bank)))
continue;
threshold_remove_bank(cpu, bank);
@@ -1431,14 +1431,14 @@ int mce_threshold_create_device(unsigned int cpu)
if (bp)
return 0;

- bp = kcalloc(mca_cfg.banks, sizeof(struct threshold_bank *),
+ bp = kcalloc(per_cpu(num_banks, cpu), sizeof(struct threshold_bank *),
GFP_KERNEL);
if (!bp)
return -ENOMEM;

per_cpu(threshold_banks, cpu) = bp;

- for (bank = 0; bank < mca_cfg.banks; ++bank) {
+ for (bank = 0; bank < per_cpu(num_banks, cpu); ++bank) {
if (!(per_cpu(bank_map, cpu) & (1 << bank)))
continue;
err = threshold_create_bank(cpu, bank);
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 14583c5c6e12..4a066c1e8ab2 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -64,6 +64,9 @@ static DEFINE_MUTEX(mce_sysfs_mutex);

DEFINE_PER_CPU(unsigned, mce_exception_count);

+DEFINE_PER_CPU_READ_MOSTLY(u8, num_banks);
+EXPORT_PER_CPU_SYMBOL_GPL(num_banks);
+
struct mce_bank {
u64 ctl; /* subevents to enable */
bool init; /* initialise bank? */
@@ -699,7 +702,7 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
if (flags & MCP_TIMESTAMP)
m.tsc = rdtsc();

- for (i = 0; i < mca_cfg.banks; i++) {
+ for (i = 0; i < this_cpu_read(num_banks); i++) {
if (!this_cpu_read(mce_banks)[i].ctl || !test_bit(i, *b))
continue;

@@ -801,7 +804,7 @@ static int mce_no_way_out(struct mce *m, char **msg, unsigned long *validp,
char *tmp;
int i;

- for (i = 0; i < mca_cfg.banks; i++) {
+ for (i = 0; i < this_cpu_read(num_banks); i++) {
m->status = mce_rdmsrl(msr_ops.status(i));
if (!(m->status & MCI_STATUS_VAL))
continue;
@@ -1081,7 +1084,7 @@ static void mce_clear_state(unsigned long *toclear)
{
int i;

- for (i = 0; i < mca_cfg.banks; i++) {
+ for (i = 0; i < this_cpu_read(num_banks); i++) {
if (test_bit(i, toclear))
mce_wrmsrl(msr_ops.status(i), 0);
}
@@ -1138,7 +1141,7 @@ static void __mc_scan_banks(struct mce *m, struct mce *final,
struct mca_config *cfg = &mca_cfg;
int severity, i;

- for (i = 0; i < cfg->banks; i++) {
+ for (i = 0; i < this_cpu_read(num_banks); i++) {
__clear_bit(i, toclear);
if (!test_bit(i, valid_banks))
continue;
@@ -1478,15 +1481,16 @@ EXPORT_SYMBOL_GPL(mce_notify_irq);

static int __mcheck_cpu_mce_banks_init(void)
{
+ u8 n_banks = this_cpu_read(num_banks);
int i;

per_cpu(mce_banks, smp_processor_id()) =
- kcalloc(MAX_NR_BANKS, sizeof(struct mce_bank), GFP_KERNEL);
+ kcalloc(n_banks, sizeof(struct mce_bank), GFP_KERNEL);

if (!this_cpu_read(mce_banks))
return -ENOMEM;

- for (i = 0; i < MAX_NR_BANKS; i++) {
+ for (i = 0; i < n_banks; i++) {
struct mce_bank *b = &this_cpu_read(mce_banks)[i];

b->ctl = -1ULL;
@@ -1507,10 +1511,15 @@ static int __mcheck_cpu_cap_init(void)
rdmsrl(MSR_IA32_MCG_CAP, cap);

b = cap & MCG_BANKCNT_MASK;
- if (WARN_ON_ONCE(b > MAX_NR_BANKS))
+ pr_debug("CPU%d supports %d MCE banks\n", smp_processor_id(), b);
+
+ if (b > MAX_NR_BANKS) {
+ pr_warn("CPU%d: Using only %u machine check banks out of %u\n",
+ smp_processor_id(), MAX_NR_BANKS, b);
b = MAX_NR_BANKS;
+ }

- mca_cfg.banks = max(mca_cfg.banks, b);
+ this_cpu_write(num_banks, b);

if (!this_cpu_read(mce_banks)) {
int err = __mcheck_cpu_mce_banks_init();
@@ -1554,7 +1563,7 @@ static void __mcheck_cpu_init_clear_banks(void)
{
int i;

- for (i = 0; i < mca_cfg.banks; i++) {
+ for (i = 0; i < this_cpu_read(num_banks); i++) {
struct mce_bank *b = &this_cpu_read(mce_banks)[i];

if (!b->init)
@@ -1604,7 +1613,7 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)

/* This should be disabled by the BIOS, but isn't always */
if (c->x86_vendor == X86_VENDOR_AMD) {
- if (c->x86 == 15 && cfg->banks > 4) {
+ if (c->x86 == 15 && this_cpu_read(num_banks) > 4) {
/*
* disable GART TBL walk error reporting, which
* trips off incorrectly with the IOMMU & 3ware
@@ -1623,7 +1632,7 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)
* Various K7s with broken bank 0 around. Always disable
* by default.
*/
- if (c->x86 == 6 && cfg->banks > 0)
+ if (c->x86 == 6 && this_cpu_read(num_banks) > 0)
this_cpu_read(mce_banks)[0].ctl = 0;

/*
@@ -1645,7 +1654,7 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)
* valid event later, merely don't write CTL0.
*/

- if (c->x86 == 6 && c->x86_model < 0x1A && cfg->banks > 0)
+ if (c->x86 == 6 && c->x86_model < 0x1A && this_cpu_read(num_banks) > 0)
this_cpu_read(mce_banks)[0].init = 0;

/*
@@ -1871,7 +1880,7 @@ static void __mce_disable_bank(void *arg)

void mce_disable_bank(int bank)
{
- if (bank >= mca_cfg.banks) {
+ if (bank >= this_cpu_read(num_banks)) {
pr_warn(FW_BUG
"Ignoring request to disable invalid MCA bank %d.\n",
bank);
@@ -1959,7 +1968,7 @@ static void mce_disable_error_reporting(void)
{
int i;

- for (i = 0; i < mca_cfg.banks; i++) {
+ for (i = 0; i < this_cpu_read(num_banks); i++) {
struct mce_bank *b = &this_cpu_read(mce_banks)[i];

if (b->init)
@@ -2070,7 +2079,7 @@ static ssize_t show_bank(struct device *s, struct device_attribute *attr,
struct mce_bank *b;
u8 bank = attr_to_bank(attr)->bank;

- if (bank >= mca_cfg.banks)
+ if (bank >= per_cpu(num_banks, s->id))
return -EINVAL;

b = &per_cpu(mce_banks, s->id)[bank];
@@ -2088,7 +2097,7 @@ static ssize_t set_bank(struct device *s, struct device_attribute *attr,
if (kstrtou64(buf, 0, &new) < 0)
return -EINVAL;

- if (bank >= mca_cfg.banks)
+ if (bank >= per_cpu(num_banks, s->id))
return -EINVAL;

b = &per_cpu(mce_banks, s->id)[bank];
@@ -2240,7 +2249,7 @@ static int mce_device_create(unsigned int cpu)
if (err)
goto error;
}
- for (j = 0; j < mca_cfg.banks; j++) {
+ for (j = 0; j < per_cpu(num_banks, cpu); j++) {
err = device_create_file(dev, &mce_bank_devs[j].attr);
if (err)
goto error2;
@@ -2272,7 +2281,7 @@ static void mce_device_remove(unsigned int cpu)
for (i = 0; mce_device_attrs[i]; i++)
device_remove_file(dev, mce_device_attrs[i]);

- for (i = 0; i < mca_cfg.banks; i++)
+ for (i = 0; i < per_cpu(num_banks, cpu); i++)
device_remove_file(dev, &mce_bank_devs[i].attr);

device_unregister(dev);
@@ -2301,7 +2310,7 @@ static void mce_reenable_cpu(void)

if (!cpuhp_tasks_frozen)
cmci_reenable();
- for (i = 0; i < mca_cfg.banks; i++) {
+ for (i = 0; i < this_cpu_read(num_banks); i++) {
struct mce_bank *b = &this_cpu_read(mce_banks)[i];

if (b->init)
@@ -2489,8 +2498,6 @@ EXPORT_SYMBOL_GPL(mcsafe_key);

static int __init mcheck_late_init(void)
{
- pr_info("Using %d MCE banks\n", mca_cfg.banks);
-
if (mca_cfg.recovery)
static_branch_inc(&mcsafe_key);

diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
index 3f82afd0f46f..8340f8213d6b 100644
--- a/arch/x86/kernel/cpu/mce/inject.c
+++ b/arch/x86/kernel/cpu/mce/inject.c
@@ -568,12 +568,7 @@ static void do_inject(void)
static int inj_bank_set(void *data, u64 val)
{
struct mce *m = (struct mce *)data;
- u8 n_banks;
- u64 cap;
-
- /* Get bank count on target CPU so we can handle non-uniform values. */
- rdmsrl_on_cpu(m->extcpu, MSR_IA32_MCG_CAP, &cap);
- n_banks = cap & MCG_BANKCNT_MASK;
+ u8 n_banks = per_cpu(num_banks, m->extcpu);

if (val >= n_banks) {
pr_err("MCA bank %llu non-existent on CPU%d\n", val, m->extcpu);
diff --git a/arch/x86/kernel/cpu/mce/internal.h b/arch/x86/kernel/cpu/mce/internal.h
index 032d52c66616..f0078859afe3 100644
--- a/arch/x86/kernel/cpu/mce/internal.h
+++ b/arch/x86/kernel/cpu/mce/internal.h
@@ -118,7 +118,6 @@ struct mca_config {
bios_cmci_threshold : 1,
__reserved : 59;

- u8 banks;
s8 bootlog;
int tolerant;
int monarch_timeout;
@@ -127,6 +126,7 @@ struct mca_config {
};

extern struct mca_config mca_cfg;
+DECLARE_PER_CPU_READ_MOSTLY(u8, num_banks);

struct mce_vendor_flags {
/*
--
2.17.1
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