linux-kernel - Re: [PATCH V1 0/3] Revert huge-paged linear mapping and its related fixups

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Message-ID: <20230625-squire-hulk-d28483ab5ef7@spud>
Date:   Sun, 25 Jun 2023 15:16:55 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Song Shuai <songshuaishuai@...ylab.org>
Cc:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, robh+dt@...nel.org, frowand.list@...il.com,
        ajones@...tanamicro.com, alexghiti@...osinc.com,
        mpe@...erman.id.au, arnd@...db.de, rppt@...nel.org,
        samuel@...lland.org, panqinglin2020@...as.ac.cn,
        conor.dooley@...rochip.com, anup@...infault.org,
        xianting.tian@...ux.alibaba.com, anshuman.khandual@....com,
        heiko@...ech.de, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH V1 0/3] Revert huge-paged linear mapping and its related
 fixups

On Sun, Jun 25, 2023 at 10:09:28PM +0800, Song Shuai wrote:
> We have encountered these two issues about huge-paged linear mapping since v6.4-rc1: 
> 
> 1. Bug report: kernel paniced when system hibernates[1]
>   
> OpenSbi [v0.8,v1.3) set the PMP regions as !no-map, and the commit 3335068f8721 
> ("riscv: Use PUD/P4D/PGD pages for the linear mapping") mapped them in linear mapping.
> The hibernation process attempted to save/restore these mapped regions resulting in access fault.
> 
> This issue was temporarily fixed by commit ed309ce52218 ("RISC-V: mark hibernation as nonportable").
> But as Alex's RFC and Rob's response stats in another thread [2] , 
> "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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