On Mon, 2017-04-03 at 02:05:55 UTC, Michael Ellerman wrote:
> setup_initial_memory_limit() is called from early_init_devtree(), which
> runs prior to feature patching. If the kernel is built with
> CONFIG_JUMP_LABEL=y
> and CONFIG_JUMP_LABEL_FEATURE_CHECKS=y then we will potentially get the
> wrong value.
>
> If we also have CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG=y we get a warning
> and backtrace:
>
> Warning! mmu_has_feature() used prior to jump label init!
> CPU: 0 PID: 0 Comm: swapper Not tainted
> 4.11.0-rc4-gccN-next-20170331-g6af2434 #1
> Call Trace:
> [c000000000fc3d50] [c000000000a26c30] .dump_stack+0xa8/0xe8 (unreliable)
> [c000000000fc3de0] [c00000000002e6b8] .setup_initial_memory_limit+0xa4/0x104
> [c000000000fc3e60] [c000000000d5c23c] .early_init_devtree+0xd0/0x2f8
> [c000000000fc3f00] [c000000000d5d3b0] .early_setup+0x90/0x11c
> [c000000000fc3f90] [c000000000000520] start_here_multiplatform+0x68/0x80
>
> Fix it by using early_mmu_has_feature().
>
> Fixes: c12e6f24d413 ("powerpc: Add option to use jump label for
> mmu_has_feature()")
> Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
Applied to powerpc next.
https://git.kernel.org/powerpc/c/4868e3508d1934d28961f940ed6b9f
cheers
