Re: Bug report: kernel paniced when system hibernates

From: Conor Dooley <conor.dooley@microchip.com>
To: Anup Patel <anup@brainfault.org>
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>
Subject: Re: Bug report: kernel paniced when system hibernates
Date: Thu, 25 May 2023 14:55:42 +0100	[thread overview]
Message-ID: <20230525-shrapnel-precut-26500fca4a48@wendy> (raw)
In-Reply-To: <CAAhSdy06nQh4H1FP_K_-VF462mhj+F2M=4AV4QSCUGe5XVqX0g@mail.gmail.com>

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On Thu, May 25, 2023 at 07:13:11PM +0530, Anup Patel wrote:
> On Thu, May 25, 2023 at 7:08 PM Conor Dooley <conor.dooley@microchip.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)

Other SBI implementations doing the same thing doesn't make it any more
correct though, right?

> > > 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.

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