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From: Maxime Bizon <mbizon@freebox.fr>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: Fail to boot 5.15 on mpc8347 with either debug_pagealloc or nobats
Date: Sun, 5 Dec 2021 22:44:08 +0100	[thread overview]
Message-ID: <20211205214408.GC29658@sakura> (raw)
In-Reply-To: <d39825e0-6b48-5ac1-662e-26186e730eaa@csgroup.eu>



On Sunday 05 Dec 2021 à 18:11:59 (+0000), Christophe Leroy wrote:

> > Is BAT5 needed here ?
> 
> Sure it is, because that's were kernel expects lowmem to be mapped. 
> Allthough the kernel will unlikely access the 128M reserved for KASAN 
> directly, the other 128M are still needed.
> 

Yes that was my point

I'm wondering if for specific PAGE_OFFSET values, __mmu_mapin_ram()
ends using a BAT to map exactly the KASAN area, thus wasting it
because the kernel would never/rarely access it.

Or worse, it could consume the latest BAT available, and there would
be none left for the actual KASAN vm area

Maybe mmu_mapin_ram() could clamp top to KASAN phys start.

-- 
Maxime

  reply	other threads:[~2021-12-05 21:44 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <f23763d551e65d4a225ba13c7898f83853c2aeaf.camel@freebox.fr>
2021-12-03 12:49 ` Fail to boot 5.15 on mpc8347 with either debug_pagealloc or nobats Christophe Leroy
2021-12-03 18:43   ` Maxime Bizon
2021-12-04 10:01     ` Christophe Leroy
2021-12-04 14:10       ` Maxime Bizon
2021-12-04 17:42         ` Christophe Leroy
2021-12-05 16:42           ` Maxime Bizon
2021-12-05 18:11             ` Christophe Leroy
2021-12-05 21:44               ` Maxime Bizon [this message]
2021-12-06  7:03                 ` Christophe Leroy
2021-12-06  8:47                   ` Maxime Bizon
2021-12-06  9:07                     ` Christophe Leroy
2021-12-06 10:32                       ` Maxime Bizon
2021-12-06 14:22                         ` Christophe Leroy
2021-12-06 15:48                           ` Maxime Bizon
2021-12-07  5:50                             ` Christophe Leroy
2021-12-07  6:11                               ` Christophe Leroy
2021-12-12 11:21                                 ` Maxime Bizon
2021-12-07  5:54             ` Christophe Leroy
2021-12-07  9:04               ` Maxime Bizon

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