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Subject[PATCH 5/7] x86/mce/amd: Straighten CPU hotplug path
Date
From: Thomas Gleixner <tglx@linutronix.de>

mce_threshold_create_device() hotplug callback runs on the plugged in
CPU so:

- use this_cpu_read() which is faster
- pass in struct threshold_bank **bp to threshold_create_bank() and
instead of doing per-CPU accesses
- Use rdmsr_safe() instead of rdmsr_safe_on_cpu() which avoids an IPI.

No functional changes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/cpu/mce/amd.c | 32 +++++++++++++++-----------------
1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index d3c416b6052a..a33d9a1caf36 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -1223,10 +1223,10 @@ static int allocate_threshold_blocks(unsigned int cpu, struct threshold_bank *tb
u32 low, high;
int err;

- if ((bank >= per_cpu(mce_num_banks, cpu)) || (block >= NR_BLOCKS))
+ if ((bank >= this_cpu_read(mce_num_banks)) || (block >= NR_BLOCKS))
return 0;

- if (rdmsr_safe_on_cpu(cpu, address, &low, &high))
+ if (rdmsr_safe(address, &low, &high))
return 0;

if (!(high & MASK_VALID_HI)) {
@@ -1316,9 +1316,10 @@ static int __threshold_add_blocks(struct threshold_bank *b)
return err;
}

-static int threshold_create_bank(unsigned int cpu, unsigned int bank)
+static int threshold_create_bank(struct threshold_bank **bp, unsigned int cpu,
+ unsigned int bank)
{
- struct device *dev = per_cpu(mce_device, cpu);
+ struct device *dev = this_cpu_read(mce_device);
struct amd_northbridge *nb = NULL;
struct threshold_bank *b = NULL;
const char *name = get_name(bank, NULL);
@@ -1338,7 +1339,7 @@ static int threshold_create_bank(unsigned int cpu, unsigned int bank)
if (err)
goto out;

- per_cpu(threshold_banks, cpu)[bank] = b;
+ bp[bank] = b;
refcount_inc(&b->cpus);

err = __threshold_add_blocks(b);
@@ -1374,8 +1375,7 @@ static int threshold_create_bank(unsigned int cpu, unsigned int bank)
if (err)
goto out_kobj;

- per_cpu(threshold_banks, cpu)[bank] = b;
-
+ bp[bank] = b;
return 0;

out_kobj:
@@ -1487,35 +1487,33 @@ int mce_threshold_remove_device(unsigned int cpu)
*/
int mce_threshold_create_device(unsigned int cpu)
{
- unsigned int bank;
+ unsigned int numbanks, bank;
struct threshold_bank **bp;
int err;

if (!mce_flags.amd_threshold)
return 0;

- bp = per_cpu(threshold_banks, cpu);
+ bp = this_cpu_read(threshold_banks);
if (bp)
return 0;

- bp = kcalloc(per_cpu(mce_num_banks, cpu), sizeof(struct threshold_bank *),
- GFP_KERNEL);
+ numbanks = this_cpu_read(mce_num_banks);
+ bp = kcalloc(numbanks, sizeof(*bp), GFP_KERNEL);
if (!bp)
return -ENOMEM;

- per_cpu(threshold_banks, cpu) = bp;
-
- for (bank = 0; bank < per_cpu(mce_num_banks, cpu); ++bank) {
- if (!(per_cpu(bank_map, cpu) & (1 << bank)))
+ for (bank = 0; bank < numbanks; ++bank) {
+ if (!(this_cpu_read(bank_map) & (1 << bank)))
continue;
- err = threshold_create_bank(cpu, bank);
+ err = threshold_create_bank(bp, cpu, bank);
if (err)
goto out_err;
}
+ this_cpu_write(threshold_banks, bp);

if (thresholding_irq_en)
mce_threshold_vector = amd_threshold_interrupt;
-
return 0;
out_err:
mce_threshold_remove_device(cpu);
--
2.21.0
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