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From:   Anup Patel <anup@brainfault.org>
Date:   Fri, 26 May 2023 20:47:46 +0530
Message-ID: <CAAhSdy0_XqiB=1w3hnYkipPj1aF_D=z=MD2fKLxk6rb_iDdBow@mail.gmail.com>
Subject: Re: Bug report: kernel paniced when system hibernates
To:     Alexandre Ghiti <alex@ghiti.fr>
Cc:     Conor Dooley <conor@kernel.org>,
        Alexandre Ghiti <alexghiti@rivosinc.com>,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@rivosinc.com>,
        Atish Patra <atishp@atishpatra.org>,
        Conor Dooley <conor.dooley@microchip.com>,
        Anup Patel <apatel@ventanamicro.com>, robh@kernel.org,
        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 Fri, May 26, 2023 at 8:42=E2=80=AFPM Alexandre Ghiti <alex@ghiti.fr> wro=
te:
>
>
> On 26/05/2023 16:59, Conor Dooley wrote:
> > On Fri, May 26, 2023 at 03:14:33PM +0200, Alexandre Ghiti wrote:
> >> Hi everyone,
> >>
> >> On Thu, May 25, 2023 at 11:24=E2=80=AFPM Conor Dooley <conor@kernel.or=
g> wrote:
> >>> On Thu, May 25, 2023 at 01:06:04PM -0700, Atish Patra wrote:
> >>>> On Thu, May 25, 2023 at 11:39=E2=80=AFAM Conor Dooley <conor@kernel.=
org> wrote:
> >>>>> On Thu, May 25, 2023 at 11:37:40AM -0700, Atish Patra wrote:
> >>>>>
> >>>>>> Any testing of hibernation still needs to revert the patch until w=
e
> >>>>>> have the proper fix.
> >>>>> "the patch" is what exactly? I assume you don't mean depending on
> >>>>> NONPORTABLE, since that is a Kconfig option.
> >>>> Nope. Sorry I meant the commit
> >>>>
> >>>> 3335068 ("riscv: Use PUD/P4D/PGD pages for the linear mapping")
> >>> Ah, if your SBI implementation is one of the affected ones, yeah.
> >>> If not, you can just set NONPORTABLE :)
> >> @Bj=C3=B6rn T=C3=B6pel emitted the idea of excluding from the hibernat=
ion all
> >> the memory nodes in the "/reserved-memory" node
> >> (https://elixir.bootlin.com/linux/v6.4-rc1/source/Documentation/device=
tree/bindings/reserved-memory/reserved-memory.yaml):
> >> I have to admit that I don't see why it is not done by default by the
> >> kernel.
> > My understanding was that it was perfectly fine to use reserved memory
> > nodes to fence off some memory to use in device drivers etc, which then
> > may need to be saved/restored.
>
>
> Agreed, but I would say that it's up to the driver then to take care of
> that, see https://docs.kernel.org/driver-api/pm/notifiers.html

I agree, it should be drivers responsibility to save/restore the dedicated
reserved memory used by itself.

Although, I think we should at least save/restore reserved memory
regions having "reusable" property set.

Regards,
Anup

>
>
> >> Unless there is stuff in this node that needs to be "hibernated", I
> >> think that would be a very good solution since we would not rely on
> >> the name of the "internal" nodes of "/reserved-memory" (i.e.
> >> "mmode_resv").
> >>
> >> I'm digging into why it is not done by default, just wanted to have
> >> your feedback before the week-end :)