linux-kernel - Re: Bug report: kernel paniced when system hibernates

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Date:   Thu, 25 May 2023 19:13:11 +0530
From:   Anup Patel <anup@...infault.org>
To:     Conor Dooley <conor.dooley@...rochip.com>
Cc:     Anup Patel <apatel@...tanamicro.com>,
        Atish Patra <atishp@...shpatra.org>,
        Alexandre Ghiti <alex@...ti.fr>, robh@...nel.org,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        jeeheng.sia@...rfivetech.com, linux-kernel@...r.kernel.org,
        palmer@...osinc.com, leyfoon.tan@...rfivetech.com,
        mason.huo@...rfivetech.com, Guo Ren <guoren@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Song Shuai <suagrfillet@...il.com>,
        linux-riscv@...ts.infradead.org,
        Andrew Jones <ajones@...tanamicro.com>
Subject: Re: Bug report: kernel paniced when system hibernates

On Thu, May 25, 2023 at 7:08 PM Conor Dooley <conor.dooley@...rochip.com> wrote:
>
> On Thu, May 25, 2023 at 06:51:28PM +0530, Anup Patel wrote:
>
> > > We should only rely on this node name for known bad versions of opensbi
> > > IMO. Going forward, if something needs to be reserved for firmware, the
> > > firmware should make sure that it is reserved by using the property for
> > > that purpose :)
>
> > There is no issue with OpenSBI since it does the right thing by marking
> > memory as reserved in the DT. This real issue is with the kernel handling
> > of reserved memory for hibernate.
>
> I don't think we are talking about the same thing here. I meant the
> no-map property which OpenSBI does not set.

Yes, we are talking about the same thing. It's not just OpenSBI not
setting no-map property in reserved memory node because other
SBI implementations would be doing the same thing (i.e. not setting
no-map property)

Regards,
Anup

>
> > Like Atish mentioned, not just OpenSBI, there will be other entities
> > (like TSM) or some other M-mode firmware which will also reserve
> > memory in DT/ACPI so clearly kernel needs a SBI implementation
> > independent way of handling reserved memory for hibernate.
>
> > > > Another option is to use compatible string or label property to indicate
> > > > that this memory region is not to be saved/restored during hibernation.
> > > > This can be documented in RISC-V DT bindings as well as the booting guide
> > > > doc that alex was talking about.
> > >
> > > Sure, a dt-binding for sbi reserved regions doesn't immediately sound
> > > like an awful idea... But we still have to work around the borked
> > > firmware - be that disabling hibernation or using the mmode_resv node
> > > when we know that the version of OpenSBI is one of those with the
> > > problem.
>
> Did you skip over this? I was agreeing that defining a common binding for
> sbi reserved regions was a good idea.