Commit 108c6494 authored by Tony Luck's avatar Tony Luck Committed by Borislav Petkov (AMD)
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x86/mce: Dynamically size space for machine check records 



Systems with a large number of CPUs may generate a large number of
machine check records when things go seriously wrong. But Linux has
a fixed-size buffer that can only capture a few dozen errors.

Allocate space based on the number of CPUs (with a minimum value based
on the historical fixed buffer that could store 80 records).

  [ bp: Rename local var from tmpp to something more telling: gpool. ]

Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarSohil Mehta <sohil.mehta@intel.com>
Reviewed-by: default avatarAvadhut Naik <avadhut.naik@amd.com>
Link: https://lore.kernel.org/r/20240307192704.37213-1-tony.luck@intel.com
parent 4cece764

arch/x86/kernel/cpu/mce/genpool.c

+25 −15
Original line number Diff line number Diff line
@@ -16,14 +16,14 @@ 
 * used to save error information organized in a lock-less list.

 *

 * This memory pool is only to be used to save MCE records in MCE context.

 * MCE events are rare, so a fixed size memory pool should be enough. Use

 * 2 pages to save MCE events for now (~80 MCE records at most).

 * MCE events are rare, so a fixed size memory pool should be enough.

 * Allocate on a sliding scale based on number of CPUs.

 */

#define MCE_POOLSZ	(2 * PAGE_SIZE)

#define MCE_MIN_ENTRIES	80

#define MCE_PER_CPU	2



static struct gen_pool *mce_evt_pool;

static LLIST_HEAD(mce_event_llist);

static char gen_pool_buf[MCE_POOLSZ];



/*

 * Compare the record "t" with each of the records on list "l" to see if
@@ -118,22 +118,32 @@ int mce_gen_pool_add(struct mce *mce) 


static int mce_gen_pool_create(void)

{

	struct gen_pool *tmpp;

	int mce_numrecords, mce_poolsz, order;

	struct gen_pool *gpool;

	int ret = -ENOMEM;

	void *mce_pool;



	tmpp = gen_pool_create(ilog2(sizeof(struct mce_evt_llist)), -1);

	if (!tmpp)

		goto out;

	order = order_base_2(sizeof(struct mce_evt_llist));

	gpool = gen_pool_create(order, -1);

	if (!gpool)

		return ret;



	ret = gen_pool_add(tmpp, (unsigned long)gen_pool_buf, MCE_POOLSZ, -1);

	mce_numrecords = max(MCE_MIN_ENTRIES, num_possible_cpus() * MCE_PER_CPU);

	mce_poolsz = mce_numrecords * (1 << order);

	mce_pool = kmalloc(mce_poolsz, GFP_KERNEL);

	if (!mce_pool) {

		gen_pool_destroy(gpool);

		return ret;

	}

	ret = gen_pool_add(gpool, (unsigned long)mce_pool, mce_poolsz, -1);

	if (ret) {

		gen_pool_destroy(tmpp);

		goto out;

		gen_pool_destroy(gpool);

		kfree(mce_pool);

		return ret;

	}



	mce_evt_pool = tmpp;

	mce_evt_pool = gpool;



out:

	return ret;

}