Re: Bug report: kernel paniced when system hibernates

[Alexandre Ghiti]

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 PM Conor Dooley <conor@xxxxxxxxxx> wrote:
> > > On Thu, May 25, 2023 at 01:06:04PM -0700, Atish Patra wrote:
> > > > On Thu, May 25, 2023 at 11:39 AM Conor Dooley <conor@xxxxxxxxxx> 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 we
> > > > > > 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 :)
> > @Björn Töpel emitted the idea of excluding from the hibernation all
> > the memory nodes in the "/reserved-memory" node
> > (https://elixir.bootlin.com/linux/v6.4-rc1/source/Documentation/devicetree/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


> > 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 :)