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Subject[PATCH 3/7] x86/mce/amd: Protect a not-fully initialized bank from the thresholding interrupt
Date
From: Thomas Gleixner <tglx@linutronix.de>

Make sure the thresholding bank descriptor is fully initialized when the
thresholding interrupt fires after a hotplug event.

[ bp: Write commit message and document long-forgotten bank_map. ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/cpu/mce/amd.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index c3b3326ad4ac..563942157758 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -192,7 +192,12 @@ EXPORT_SYMBOL_GPL(smca_banks);
static char buf_mcatype[MAX_MCATYPE_NAME_LEN];

static DEFINE_PER_CPU(struct threshold_bank **, threshold_banks);
-static DEFINE_PER_CPU(unsigned int, bank_map); /* see which banks are on */
+
+/*
+ * A list of the banks enabled on each logical CPU. Controls which respective
+ * descriptors to initialize later in mce_threshold_create_device().
+ */
+static DEFINE_PER_CPU(unsigned int, bank_map);

/* Map of banks that have more than MCA_MISC0 available. */
static DEFINE_PER_CPU(u32, smca_misc_banks_map);
@@ -1016,13 +1021,22 @@ static void log_and_reset_block(struct threshold_block *block)
static void amd_threshold_interrupt(void)
{
struct threshold_block *first_block = NULL, *block = NULL, *tmp = NULL;
+ struct threshold_bank **bp = this_cpu_read(threshold_banks);
unsigned int bank, cpu = smp_processor_id();

+ /*
+ * Validate that the threshold bank has been initialized already. The
+ * handler is installed at boot time, but on a hotplug event the
+ * interrupt might fire before the data has been initialized.
+ */
+ if (!bp)
+ return;
+
for (bank = 0; bank < this_cpu_read(mce_num_banks); ++bank) {
if (!(per_cpu(bank_map, cpu) & (1 << bank)))
continue;

- first_block = per_cpu(threshold_banks, cpu)[bank]->blocks;
+ first_block = bp[bank]->blocks;
if (!first_block)
continue;

@@ -1247,6 +1261,7 @@ static int allocate_threshold_blocks(unsigned int cpu, struct threshold_bank *tb

INIT_LIST_HEAD(&b->miscj);

+ /* This is safe as @tb is not visible yet */
if (tb->blocks)
list_add(&b->miscj, &tb->blocks->miscj);
else
--
2.21.0
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