linux-kernel - Re: linux-next: build failure after merge of the bpf-next tree

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Message-ID: <CAADnVQKotSrp8CkVpFw-y800NJ_R7An-iw-twrQZaOdYUeRtqQ@mail.gmail.com>
Date: Tue, 18 Mar 2025 19:46:52 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Stephen Rothwell <sfr@...b.auug.org.au>, Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc: Daniel Borkmann <daniel@...earbox.net>, Alexei Starovoitov <ast@...nel.org>, 
	Andrii Nakryiko <andrii@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Uros Bizjak <ubizjak@...il.com>, bpf <bpf@...r.kernel.org>, 
	Networking <netdev@...r.kernel.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, 
	Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: build failure after merge of the bpf-next tree

On Tue, Mar 18, 2025 at 7:33 PM Stephen Rothwell <sfr@...b.auug.org.au> wrote:
>
> Hi all,
>
> After merging the bpf-next tree, today's linux-next build (x86_64
> allmodconfig) failed like this:
>
> In file included from include/asm-generic/percpu.h:7,
>                  from arch/x86/include/asm/percpu.h:630,
>                  from arch/x86/include/asm/preempt.h:6,
>                  from include/linux/preempt.h:79,
>                  from include/linux/smp.h:116,
>                  from kernel/locking/qspinlock.c:16:
> kernel/locking/qspinlock.h: In function 'decode_tail':
> include/linux/percpu-defs.h:219:45: error: initialization from pointer to non-enclosed address space
>   219 |         const void __percpu *__vpp_verify = (typeof((ptr) + 0))NULL;    \
>       |                                             ^
> include/linux/percpu-defs.h:237:9: note: in expansion of macro '__verify_pcpu_ptr'
>   237 |         __verify_pcpu_ptr(ptr);                                         \
>       |         ^~~~~~~~~~~~~~~~~
> kernel/locking/qspinlock.h:67:16: note: in expansion of macro 'per_cpu_ptr'
>    67 |         return per_cpu_ptr(&qnodes[idx].mcs, cpu);
>       |                ^~~~~~~~~~~
> include/linux/percpu-defs.h:219:45: note: expected 'const __seg_gs void *' but pointer is of type 'struct mcs_spinlock *'
>   219 |         const void __percpu *__vpp_verify = (typeof((ptr) + 0))NULL;    \
>       |                                             ^
> include/linux/percpu-defs.h:237:9: note: in expansion of macro '__verify_pcpu_ptr'
>   237 |         __verify_pcpu_ptr(ptr);                                         \
>       |         ^~~~~~~~~~~~~~~~~
> kernel/locking/qspinlock.h:67:16: note: in expansion of macro 'per_cpu_ptr'
>    67 |         return per_cpu_ptr(&qnodes[idx].mcs, cpu);
>       |                ^~~~~~~~~~~
> kernel/locking/qspinlock.c: In function 'native_queued_spin_lock_slowpath':
> kernel/locking/qspinlock.c:285:41: error: passing argument 2 of 'decode_tail' from pointer to non-enclosed address space
>   285 |                 prev = decode_tail(old, qnodes);
>       |                                         ^~~~~~
> In file included from kernel/locking/qspinlock.c:30:
> kernel/locking/qspinlock.h:62:79: note: expected 'struct qnode *' but argument is of type '__seg_gs struct qnode *'
>    62 | static inline __pure struct mcs_spinlock *decode_tail(u32 tail, struct qnode *qnodes)
>       |                                                                 ~~~~~~~~~~~~~~^~~~~~
> In file included from kernel/locking/qspinlock.c:401:
> kernel/locking/qspinlock.c: In function '__pv_queued_spin_lock_slowpath':
> kernel/locking/qspinlock.c:285:41: error: passing argument 2 of 'decode_tail' from pointer to non-enclosed address space
>   285 |                 prev = decode_tail(old, qnodes);
>       |                                         ^~~~~~
> kernel/locking/qspinlock.h:62:79: note: expected 'struct qnode *' but argument is of type '__seg_gs struct qnode *'
>    62 | static inline __pure struct mcs_spinlock *decode_tail(u32 tail, struct qnode *qnodes)
>       |                                                                 ~~~~~~~~~~~~~~^~~~~~
>
> Caused by the resilient-queued-spin-lock branch of the bpf-next tree
> interacting with the "Enable strict percpu address space checks" series
> form the mm-stable tree.

Do you mean this set:
https://lore.kernel.org/all/20250127160709.80604-1-ubizjak@gmail.com/

>
> I don't know why this happens, but reverting that branch inf the bpf-next
> tree makes the failure go away, so I have done that for today.

Kumar,

pls take a look.