x86/mce/amd: Straighten CPU hotplug path

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>
Link: https://lkml.kernel.org/r/20200403161943.1458-6-bp@alien8.de

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index d3c416b..a33d9a1 100644 (file)
--- 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);