Re: [PATCH] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG

On Fri, 1 Jul 2022 08:06:15 +0200, Christophe Leroy wrote:

Since commit 4291d085b0b0 ("powerpc/32s: Make pte_update() non
atomic on 603 core"), pte_update() has been using
mmu_has_feature(MMU_FTR_HPTE_TABLE) to avoid a useless atomic
operation on 603 cores.

When kasan_early_init() sets up the early zero shadow, it uses
__set_pte_at(). On book3s/32, __set_pte_at() calls pte_update()
when CONFIG_SMP is selected in order to ensure the preservation of
_PAGE_HASHPTE in case of concurrent update of the PTE. But that's
too early for mmu_has_feature(), so when
CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG is selected, mmu_has_feature()
calls printk(). That's too early to call printk() because KASAN
early zero shadow page is not set up yet. It leads to a deadlock.

[...]

Applied to powerpc/next.

[1/1] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG
      https://git.kernel.org/powerpc/c/6042a1652d643d1d34fa89bb314cb102960c0800

cheers