Subject: Re: "test_ip_fast_csum: ASSERTION FAILED at lib/checksum_kunit.c:589" at boot with CONFIG_CHECKSUM_KUNIT=y enabled on a Talos II, kernel 6.8-rc5

From: Erhard Furtner <[email-masked]>
Date: Fri, 23 Feb 2024 12:37:13 +0100

On Fri, 23 Feb 2024 09:06:56 +0000
Christophe Leroy <[email-masked]> wrote:

> Yes, with second patch is magically works, meaning the patch description 
> is not correct because the problem for powerpc it not at all related to 
> memory alignment but to endianness. And endianness should have been 
> fixed by patch 1, but instead of it, patch 1 just hides the problem by 
> forcing casts.
> 
> The real fix for endianness which should be your patch 1 is the 
> following change. With that change it works perfectly well without any 
> forced cast:
> 
> diff --git a/lib/checksum_kunit.c b/lib/checksum_kunit.c
> index 225bb7701460..bf70850035c7 100644
> --- a/lib/checksum_kunit.c
> +++ b/lib/checksum_kunit.c
> @@ -215,7 +215,7 @@ static const u32 init_sums_no_overflow[] = {
>   	0xffff0000, 0xfffffffb,
>   };
> 
> -static const __sum16 expected_csum_ipv6_magic[] = {
> +static const u16 expected_csum_ipv6_magic[] = {
>   	0x18d4, 0x3085, 0x2e4b, 0xd9f4, 0xbdc8, 0x78f,	0x1034, 0x8422, 0x6fc0,
>   	0xd2f6, 0xbeb5, 0x9d3,	0x7e2a, 0x312e, 0x778e, 0xc1bb, 0x7cf2, 0x9d1e,
>   	0xca21, 0xf3ff, 0x7569, 0xb02e, 0xca86, 0x7e76, 0x4539, 0x45e3, 0xf28d,
> @@ -241,7 +241,7 @@ static const __sum16 expected_csum_ipv6_magic[] = {
>   	0x3845, 0x1014
>   };
> 
> -static const __sum16 expected_fast_csum[] = {
> +static const u16 expected_fast_csum[] = {
>   	0xda83, 0x45da, 0x4f46, 0x4e4f, 0x34e,	0xe902, 0xa5e9, 0x87a5, 0x7187,
>   	0x5671, 0xf556, 0x6df5, 0x816d, 0x8f81, 0xbb8f, 0xfbba, 0x5afb, 0xbe5a,
>   	0xedbe, 0xabee, 0x6aac, 0xe6b,	0xea0d, 0x67ea, 0x7e68, 0x8a7e, 0x6f8a,
> @@ -577,7 +577,8 @@ static void test_csum_no_carry_inputs(struct kunit 
> *test)
> 
>   static void test_ip_fast_csum(struct kunit *test)
>   {
> -	__sum16 csum_result, expected;
> +	__sum16 csum_result;
> +	u16 expected;
> 
>   	for (int len = IPv4_MIN_WORDS; len < IPv4_MAX_WORDS; len++) {
>   		for (int index = 0; index < NUM_IP_FAST_CSUM_TESTS; index++) {
> @@ -586,7 +587,7 @@ static void test_ip_fast_csum(struct kunit *test)
>   				expected_fast_csum[(len - IPv4_MIN_WORDS) *
>   						   NUM_IP_FAST_CSUM_TESTS +
>   						   index];
> -			CHECK_EQ(expected, csum_result);
> +			CHECK_EQ(to_sum16(expected), csum_result);
>   		}
>   	}
>   }
> @@ -598,7 +599,7 @@ static void test_csum_ipv6_magic(struct kunit *test)
>   	const struct in6_addr *daddr;
>   	unsigned int len;
>   	unsigned char proto;
> -	unsigned int csum;
> +	__wsum csum;
> 
>   	const int daddr_offset = sizeof(struct in6_addr);
>   	const int len_offset = sizeof(struct in6_addr) + sizeof(struct in6_addr);
> @@ -611,10 +612,10 @@ static void test_csum_ipv6_magic(struct kunit *test)
>   		saddr = (const struct in6_addr *)(random_buf + i);
>   		daddr = (const struct in6_addr *)(random_buf + i +
>   						  daddr_offset);
> -		len = *(unsigned int *)(random_buf + i + len_offset);
> +		len = le32_to_cpu(*(__le32 *)(random_buf + i + len_offset));
>   		proto = *(random_buf + i + proto_offset);
> -		csum = *(unsigned int *)(random_buf + i + csum_offset);
> -		CHECK_EQ(expected_csum_ipv6_magic[i],
> +		csum = *(__wsum *)(random_buf + i + csum_offset);
> +		CHECK_EQ(to_sum16(expected_csum_ipv6_magic[i]),
>   			 csum_ipv6_magic(saddr, daddr, len, proto, csum));
>   	}
>   #endif /* !CONFIG_NET */
> ---
> 
> Christophe

Your patch applied on top of 6.8-rc5 fixes the issue. Thanks!

And I take your remarks here as a hint for the other "drm_test_fb_xrgb8888_to_xrgb2101010 on Big Endian machines" issue I posted. ;) Let's see what I can do.

Regards,
Erhard