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In-Reply-To: <20230525-postnasal-monopoly-98adb96ffaa1@wendy>
From:   Anup Patel <anup@brainfault.org>
Date:   Thu, 25 May 2023 19:13:11 +0530
Message-ID: <CAAhSdy06nQh4H1FP_K_-VF462mhj+F2M=4AV4QSCUGe5XVqX0g@mail.gmail.com>
Subject: Re: Bug report: kernel paniced when system hibernates
To:     Conor Dooley <conor.dooley@microchip.com>
Cc:     Anup Patel <apatel@ventanamicro.com>,
        Atish Patra <atishp@atishpatra.org>,
        Alexandre Ghiti <alex@ghiti.fr>, robh@kernel.org,
        Alexandre Ghiti <alexghiti@rivosinc.com>,
        jeeheng.sia@starfivetech.com, linux-kernel@vger.kernel.org,
        palmer@rivosinc.com, leyfoon.tan@starfivetech.com,
        mason.huo@starfivetech.com, Guo Ren <guoren@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Song Shuai <suagrfillet@gmail.com>,
        linux-riscv@lists.infradead.org,
        Andrew Jones <ajones@ventanamicro.com>
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On Thu, May 25, 2023 at 7:08=E2=80=AFPM Conor Dooley <conor.dooley@microchi=
p.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 opens=
bi
> > > IMO. Going forward, if something needs to be reserved for firmware, t=
he
> > > firmware should make sure that it is reserved by using the property f=
or
> > > 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 handli=
ng
> > 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 ind=
icate
> > > > that this memory region is not to be saved/restored during hibernat=
ion.
> > > > 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.