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Date:   Sun, 25 Jun 2023 15:16:55 +0100
From:   Conor Dooley <conor@kernel.org>
To:     Song Shuai <songshuaishuai@tinylab.org>
Cc:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, robh+dt@kernel.org, frowand.list@gmail.com,
        ajones@ventanamicro.com, alexghiti@rivosinc.com,
        mpe@ellerman.id.au, arnd@arndb.de, rppt@kernel.org,
        samuel@sholland.org, panqinglin2020@iscas.ac.cn,
        conor.dooley@microchip.com, anup@brainfault.org,
        xianting.tian@linux.alibaba.com, anshuman.khandual@arm.com,
        heiko@sntech.de, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [PATCH V1 0/3] Revert huge-paged linear mapping and its related
 fixups
Message-ID: <20230625-squire-hulk-d28483ab5ef7@spud>
References: <20230625140931.1266216-1-songshuaishuai@tinylab.org>
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On Sun, Jun 25, 2023 at 10:09:28PM +0800, Song Shuai wrote:
> We have encountered these two issues about huge-paged linear mapping sinc=
e v6.4-rc1:=20
>=20
> 1. Bug report: kernel paniced when system hibernates[1]
>  =20
> OpenSbi [v0.8,v1.3) set the PMP regions as !no-map, and the commit 333506=
8f8721=20
> ("riscv: Use PUD/P4D/PGD pages for the linear mapping") mapped them in li=
near mapping.
> The hibernation process attempted to save/restore these mapped regions re=
sulting in access fault.
>=20
> This issue was temporarily fixed by commit ed309ce52218 ("RISC-V: mark hi=
bernation as nonportable").
> But as Alex's RFC and Rob's response stats in another thread [2] ,=20
> "Hibernation is only one case. Speculative accesses could also occur."
> So this fixing commit seems not the perfect answer to this issue.

This is a misunderstanding, I was not attempting to fix the issue, but
rather buy time to fix the problem properly, without regressing support
for hibernation when we do.

Cheers,
Conor.


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