Le 10/10/2022 à 16:10, Nathan Lynch a écrit :

Michael Ellerman [off-list ref] writes:

quoted

Christophe Leroy [off-list ref] writes:

quoted

+ KASAN list

Le 06/10/2022 à 06:10, Michael Ellerman a écrit :

quoted

Nathan Lynch [off-list ref] writes:

quoted

kasan is known to crash at boot on book3s_64 with non-radix MMU. As
noted in commit 41b7a347bf14 ("powerpc: Book3S 64-bit outline-only
KASAN support"):

    A kernel with CONFIG_KASAN=y will crash during boot on a machine
    using HPT translation because not all the entry points to the
    generic KASAN code are protected with a call to kasan_arch_is_ready().

I guess I thought there was some plan to fix that.

I was thinking the same.

Do we have a list of the said entry points to the generic code that are
lacking a call to kasan_arch_is_ready() ?

Typically, the BUG dump below shows that kasan_byte_accessible() is
lacking the check. It should be straight forward to add
kasan_arch_is_ready() check to kasan_byte_accessible(), shouldn't it ?

Yes :)

And one other spot, but the patch below boots OK for me. I'll leave it
running for a while just in case there's a path I've missed.

It works for me too, thanks (p8 pseries qemu).

This avoids the boot-time oops, but kasan remains unimplemented for hash
mmu. Raising the question: with the trivial crashes addressed, is the
current message ('KASAN not enabled as it requires radix!') sufficient
to notify developers (such as me, a week ago) who mean to use kasan on a
book3s platform, unaware that it's radix-only? Would a WARN or something
more prominent still be justified?

I guess people will figure it out as soon as they think to search the
kernel log for 'KASAN'...

I don't think the big hammer WARN would be justified.
WARN is supposed to be used only with unexpected conditions.

KASAN not working with hash-MMU is expected. A pr_warn() should be enough.

Someone who has a kernel with KASAN built in but who is not interested 
by KASAN and who is booting it one a HASH-MMU will be terrified by a WARN.