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From:   Michael Ellerman <patch-notifications@ellerman.id.au>
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>
Cc:     linuxppc-dev@lists.ozlabs.org,
        Erhard Furtner <erhard_f@mailbox.org>,
        linux-kernel@vger.kernel.org
In-Reply-To: <2ee707512b8b212b079b877f4ceb525a1606a3fb.1656655567.git.christophe.leroy@csgroup.eu>
References: <2ee707512b8b212b079b877f4ceb525a1606a3fb.1656655567.git.christophe.leroy@csgroup.eu>
Subject: Re: [PATCH] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG
Message-Id: <165909975339.253830.11928843532091953158.b4-ty@ellerman.id.au>
Date:   Fri, 29 Jul 2022 23:02:33 +1000
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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