linux-kernel - Re: [PATCH v2] RDMA/irdma: switch to using the crc32c library

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Message-ID: <20250209154416.GA1230@sol.localdomain>
Date: Sun, 9 Feb 2025 07:44:16 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: Leon Romanovsky <leon@...nel.org>
Cc: Mustafa Ismail <mustafa.ismail@...el.com>,
	Tatyana Nikolova <tatyana.e.nikolova@...el.com>,
	Jason Gunthorpe <jgg@...pe.ca>, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] RDMA/irdma: switch to using the crc32c library

On Sun, Feb 09, 2025 at 11:12:55AM +0200, Leon Romanovsky wrote:
> On Thu, Feb 06, 2025 at 07:57:50PM -0800, Eric Biggers wrote:
> > On Thu, Feb 06, 2025 at 07:36:43PM -0800, Eric Biggers wrote:
> > > +int irdma_ieq_check_mpacrc(const void *addr, u32 len, u32 val)
> > >  {
> > > -	u32 crc = 0;
> > > -
> > > -	crypto_shash_digest(desc, addr, len, (u8 *)&crc);
> > > -	if (crc != val)
> > > +	if (~crc32c(~0, addr, len) != val)
> > >  		return -EINVAL;
> > >  
> > >  	return 0;
> > >  }
> > 
> > Sorry, I just realized this isn't actually equivalent on big endian CPUs, since
> > the byte array produced by crypto_shash_digest() used little endian byte order,
> > whereas crc32c() just returns a CPU endian value.
> > 
> > And of course this broken subsystem uses u32 for the little endian values
> > instead of __le32 like the result of the kernel.
> > 
> > Not sure it's worth my time to continue to try to fix this subsystem properly.
> 
> There is no need to be such dramatic. You are not fixing anything by
> switch to new APIs

Exactly.  That's because I dropped the patches that actually did fix real
endianness bugs, because of the pointless pushback I received -- see
https://lore.kernel.org/linux-rdma/20250127223840.67280-1-ebiggers@kernel.org/T/#u

- Eric