* Qian Cai <cai@xxxxxx> wrote:
> The commit 108c14858b9e ("locking/lockdep: Add support for dynamic
> keys") introduced a boot warning on powerpc below, because since the
> commit 2d4f567103ff ("KVM: PPC: Introduce kvm_tmp framework") adds
> kvm_tmp[] into the .bss section and then free the rest of unused spaces
> back to the page allocator.
>
> kernel_init
> kvm_guest_init
> kvm_free_tmp
> free_reserved_area
> free_unref_page
> free_unref_page_prepare
>
> Later, alloc_workqueue() happens to allocate some pages from there and
> trigger the warning at,
>
> if (WARN_ON_ONCE(static_obj(key)))
>
> Fix it by adding a generic helper arch_is_bss_hole() to skip those areas
> in static_obj(). Since kvm_free_tmp() is only done early during the
> boot, just go lockless to make the implementation simple for now.
>
> WARNING: CPU: 0 PID: 13 at kernel/locking/lockdep.c:1120
> Workqueue: events work_for_cpu_fn
> Call Trace:
> lockdep_register_key+0x68/0x200
> wq_init_lockdep+0x40/0xc0
> trunc_msg+0x385f9/0x4c30f (unreliable)
> wq_init_lockdep+0x40/0xc0
> alloc_workqueue+0x1e0/0x620
> scsi_host_alloc+0x3d8/0x490
> ata_scsi_add_hosts+0xd0/0x220 [libata]
> ata_host_register+0x178/0x400 [libata]
> ata_host_activate+0x17c/0x210 [libata]
> ahci_host_activate+0x84/0x250 [libahci]
> ahci_init_one+0xc74/0xdc0 [ahci]
> local_pci_probe+0x78/0x100
> work_for_cpu_fn+0x40/0x70
> process_one_work+0x388/0x750
> process_scheduled_works+0x50/0x90
> worker_thread+0x3d0/0x570
> kthread+0x1b8/0x1e0
> ret_from_kernel_thread+0x5c/0x7c
>
> Fixes: 108c14858b9e ("locking/lockdep: Add support for dynamic keys")
> Signed-off-by: Qian Cai <cai@xxxxxx>
> ---
>
> v2: No need to actually define arch_is_bss_hole() powerpc64 only.
>
> arch/powerpc/include/asm/sections.h | 11 +++++++++++
> arch/powerpc/kernel/kvm.c | 5 +++++
> include/asm-generic/sections.h | 7 +++++++
> kernel/locking/lockdep.c | 3 +++
> 4 files changed, 26 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 4a1664a8658d..4f5d69c42017 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -5,8 +5,19 @@
>
> #include <linux/elf.h>
> #include <linux/uaccess.h>
> +
> +#define arch_is_bss_hole arch_is_bss_hole
> +
> #include <asm-generic/sections.h>
>
> +extern void *bss_hole_start, *bss_hole_end;
> +
> +static inline int arch_is_bss_hole(unsigned long addr)
> +{
> + return addr >= (unsigned long)bss_hole_start &&
> + addr < (unsigned long)bss_hole_end;
> +}
> +
> extern char __head_end[];
>
> #ifdef __powerpc64__
> diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
> index b7b3a5e4e224..89e0e522e125 100644
> --- a/arch/powerpc/kernel/kvm.c
> +++ b/arch/powerpc/kernel/kvm.c
> @@ -66,6 +66,7 @@
> static bool kvm_patching_worked = true;
> char kvm_tmp[1024 * 1024];
> static int kvm_tmp_index;
> +void *bss_hole_start, *bss_hole_end;
>
> static inline void kvm_patch_ins(u32 *inst, u32 new_inst)
> {
> @@ -707,6 +708,10 @@ static __init void kvm_free_tmp(void)
> */
> kmemleak_free_part(&kvm_tmp[kvm_tmp_index],
> ARRAY_SIZE(kvm_tmp) - kvm_tmp_index);
> +
> + bss_hole_start = &kvm_tmp[kvm_tmp_index];
> + bss_hole_end = &kvm_tmp[ARRAY_SIZE(kvm_tmp)];
> +
> free_reserved_area(&kvm_tmp[kvm_tmp_index],
> &kvm_tmp[ARRAY_SIZE(kvm_tmp)], -1, NULL);
> }
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index d1779d442aa5..4d8b1f2c5fd9 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -91,6 +91,13 @@ static inline int arch_is_kernel_initmem_freed(unsigned long addr)
> }
> #endif
>
> +#ifndef arch_is_bss_hole
> +static inline int arch_is_bss_hole(unsigned long addr)
> +{
> + return 0;
> +}
> +#endif
> +
> /**
> * memory_contains - checks if an object is contained within a memory region
> * @begin: virtual address of the beginning of the memory region
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 4861cf8e274b..cd75b51f15ce 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -675,6 +675,9 @@ static int static_obj(const void *obj)
> if (arch_is_kernel_initmem_freed(addr))
> return 0;
>
> + if (arch_is_bss_hole(addr))
> + return 0;
arch_is_bss_hole() should use a 'bool' - but other than that, this
looks good to me, if the PowerPC maintainers agree too.
Thanks,
Ingo
