On Mon, 2017-07-17 at 21:31 +1000, Michael Ellerman wrote:
> In commit 1c0eaf0f56d6 ("powerpc/powernv: Tell OPAL about our MMU mode
> on POWER9"), we added additional flags to the OPAL call to configure
> CPUs at boot.
>
> These flags only work on Power9 firmwares, and worse can cause boot
> failures on Power8 machines, so we check for CPU_FTR_ARCH_300 (aka POWER9)
> before adding the extra flags.
>
> Unfortunately we forgot that opal_configure_cores() is called before
> the CPU feature checks are dynamically patched, meaning the check
> always returns true.
>
> We definitely need to do something to make the CPU feature checks less
> prone to bugs like this, but for now the minimal fix is to use
> early_cpu_has_feature().
>
> Reported-and-tested-by: Abdul Haleem <abdha...@linux.vnet.ibm.com>
> Fixes: 1c0eaf0f56d6 ("powerpc/powernv: Tell OPAL about our MMU mode on
> POWER9")
> Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
> ---
> arch/powerpc/platforms/powernv/opal.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/opal.c
> b/arch/powerpc/platforms/powernv/opal.c
> index 9b87abb178f0..cad6b57ce494 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -78,7 +78,7 @@ void opal_configure_cores(void)
> * ie. Host hash supports hash guests
> * Host radix supports hash/radix guests
> */
> - if (cpu_has_feature(CPU_FTR_ARCH_300)) {
> + if (early_cpu_has_feature(CPU_FTR_ARCH_300)) {
> reinit_flags |= OPAL_REINIT_CPUS_MMU_HASH;
> if (early_radix_enabled())
> reinit_flags |= OPAL_REINIT_CPUS_MMU_RADIX;
We do have CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG, but I am not sure if there
is an efficient way to enable it till we actually get the key enabled. I wonder
if a branch hint will help, but I still feel its expensive.
Acked-by: Balbir Singh <bsinghar...@gmail.com>
