Re: [sparc64] crc32c misbehave

From: Anatoly Pugachev <redacted>
Date: Wed, 31 May 2017 14:56:52 +0300

While debugging occasional crc32c checksum errors with xfs disk reads on
sparc64 (T5 [sun4v] 3.6 GHz CPU ldom, debian unstable/sid), Eric have found
that crc32c sometimes returns wrong checksum for data. Eric made a simple
test kernel module (included), which produce the following results on my
sparc64 machines:

I don't think that crc32c() is thread safe because of the way it is
implemented with a shared TFM crypto object allocated once at boot
time.

I think you are seeing the corruption any time an interrupt comes in
on the same cpu as your test module is running on and does a crc32c()
calculation, corrupting the context key value being used by your
invocation.

At least that's my guess, I could have misread how the key is stored
and managed around operations.

Can you try something like disabling cpu IRQs around the crc32c() function
in lib/libcrc32c.c?  Something like:

	u32 retval;

	local_irq_disable();

	shash->tfm = tfm;
	shash->flags = 0;
	*ctx = crc;

	err = crypto_shash_update(shash, address, length);
	BUG_ON(err);

	retval = *ctx;

	local_irq_enable();

	return retval;

Thanks.