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Date:   Wed, 15 Nov 2023 22:59:17 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     David Howells <dhowells@redhat.com>,
        kernel test robot <oliver.sang@intel.com>,
        oe-lkp@lists.linux.dev, lkp@intel.com,
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        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
        Christian Brauner <christian@brauner.io>,
        Matthew Wilcox <willy@infradead.org>,
        David Laight <David.Laight@aculab.com>, ying.huang@intel.com,
        feng.tang@intel.com, fengwei.yin@intel.com
Subject: Re: [linus:master] [iov_iter] c9eec08bac: vm-scalability.throughput
 -16.9% regression
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On Wed, Nov 15, 2023 at 04:50:06PM -0500, Linus Torvalds wrote:
> Sadly, we don't seem to have any obvious #define for "this is not real
> kernel code". We just have a lot of ad-hoc tricks, like removing
> compiler flags and disabling things like KASAN etc on a file-by-file
> (or directory) basis.

Yeah, "untangling" memcpy() has always been a PITA, every time I tried
it. So I'd need to come up with a somewhat sensible scheme of "use this
special memcpy() only in kernel code proper and fallback to the library
version or gcc builtin otherwise"...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette