Re: [PATCH V1 1/3] Revert "RISC-V: mark hibernation as nonportable"

From: Conor Dooley <conor@kernel.org>
To: Song Shuai <songshuaishuai@tinylab.org>
Cc: paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, robh+dt@kernel.org,
	frowand.list@gmail.com, ajones@ventanamicro.com,
	alexghiti@rivosinc.com, mpe@ellerman.id.au, arnd@arndb.de,
	rppt@kernel.org, samuel@sholland.org, panqinglin2020@iscas.ac.cn,
	conor.dooley@microchip.com, anup@brainfault.org,
	xianting.tian@linux.alibaba.com, anshuman.khandual@arm.com,
	heiko@sntech.de, linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [PATCH V1 1/3] Revert "RISC-V: mark hibernation as nonportable"
Date: Sun, 25 Jun 2023 15:18:49 +0100	[thread overview]
Message-ID: <20230625-multiple-diaper-1db88a75314e@spud> (raw)
In-Reply-To: <20230625140931.1266216-2-songshuaishuai@tinylab.org>

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On Sun, Jun 25, 2023 at 10:09:29PM +0800, Song Shuai wrote:
> This reverts commit ed309ce522185583b163bd0c74f0d9f299fe1826.
> 
> With the commit 3335068f8721 ("riscv: Use PUD/P4D/PGD pages for the
> linear mapping") reverted, the MIN_MEMBLOCK_ADDR points the kernel
> load address which was placed at a PMD boundary.

> And firmware always
> correctly mark resident memory, or memory protected with PMP as
> per the devicetree specification and/or the UEFI specification.

But this is not true? The versions of OpenSBI that you mention in your
cover letter do not do this.
Please explain.

> So those regions will not be mapped in the linear mapping and they
> can be safely saved/restored by hibernation.
> 
> Signed-off-by: Song Shuai <songshuaishuai@tinylab.org>
> ---
>  arch/riscv/Kconfig | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 5966ad97c30c..17b5fc7f54d4 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -800,11 +800,8 @@ menu "Power management options"
>  
>  source "kernel/power/Kconfig"
>  
> -# Hibernation is only possible on systems where the SBI implementation has
> -# marked its reserved memory as not accessible from, or does not run
> -# from the same memory as, Linux
>  config ARCH_HIBERNATION_POSSIBLE
> -	def_bool NONPORTABLE
> +	def_bool y
>  
>  config ARCH_HIBERNATION_HEADER
>  	def_bool HIBERNATION
> -- 
> 2.20.1
> 

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