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From: Charlemagne Lasse <charlemagnelasse@gmail.com>
Date: Sat, 30 Mar 2024 00:56:54 +0100
Message-ID: <CAFGhKbzev7W4aHwhFPWwMZQEHenVgZUj7=aunFieVqZg3mt14A@mail.gmail.com>
Subject: warning: cast removes address space '__percpu' of expression
To: x86@kernel.org, LKML <linux-kernel@vger.kernel.org>, 
	Luc Van Oostenryck <lucvoo@kernel.org>
Cc: Uros Bizjak <ubizjak@gmail.com>, Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@kernel.org>, 
	Nadav Amit <namit@vmware.com>, Brian Gerst <brgerst@gmail.com>, 
	Denys Vlasenko <dvlasenk@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>, 
	Linus Torvalds <torvalds@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>, 
	Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>, Josh Poimboeuf <jpoimboe@redhat.com>
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After switching to linux 6.9-rc1, I get a lot of these errors (when
compiling with cgcc/sparse):

/include/linux/netdevice.h:4033:17: warning: cast removes address
space '__percpu' of expression

This is around code which wasn't changed and which correctly uses the
per cpu helper. Sparse flags were -Wsparse-all for sparse 0.6.4
(latest release). Sparse was enabled via C=1 parameter and sparse was
configured using CHECK="sparse -Wsparse-all"

Problem was introduced between commit 8ae292c66dcb ("x86/lib: Address
kernel-doc warnings") and 3a1d3829e193 ("x86/percpu: Avoid sparse
warning with cast to named address space").

I would even go as far as saying that 1ca3683cc6d2 ("x86/percpu:
Enable named address spaces with known compiler version") together
with 3a1d3829e193 ("x86/percpu: Avoid sparse warning with cast to
named address space") triggered this problem