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Date:   Mon, 27 Mar 2023 15:13:53 +0200
From:   Andrew Jones <ajones@ventanamicro.com>
To:     Sia Jee Heng <jeeheng.sia@starfivetech.com>
Cc:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org, leyfoon.tan@starfivetech.com,
        mason.huo@starfivetech.com
Subject: Re: [PATCH v7 0/4] RISC-V Hibernation Support
Message-ID: <20230327131353.6gzjjppfy2o5456x@orel>
References: <20230323045604.536099-1-jeeheng.sia@starfivetech.com>
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On Thu, Mar 23, 2023 at 12:56:00PM +0800, Sia Jee Heng wrote:
> This series adds RISC-V Hibernation/suspend to disk support.
> Low level Arch functions were created to support hibernation.
> swsusp_arch_suspend() relies code from __cpu_suspend_enter() to write
> cpu state onto the stack, then calling swsusp_save() to save the memory
> image.
> 
> Arch specific hibernation header is implemented and is utilized by the
> arch_hibernation_header_restore() and arch_hibernation_header_save()
> functions. The arch specific hibernation header consists of satp, hartid,
> and the cpu_resume address. The kernel built version is also need to be
> saved into the hibernation image header to making sure only the same
> kernel is restore when resume.
> 
> swsusp_arch_resume() creates a temporary page table that covering only
> the linear map. It copies the restore code to a 'safe' page, then start to
> restore the memory image. Once completed, it restores the original
> kernel's page table. It then calls into __hibernate_cpu_resume()
> to restore the CPU context. Finally, it follows the normal hibernation
> path back to the hibernation core.
> 
> To enable hibernation/suspend to disk into RISCV, the below config
> need to be enabled:
> - CONFIG_ARCH_HIBERNATION_HEADER
> - CONFIG_ARCH_HIBERNATION_POSSIBLE
> 
> At high-level, this series includes the following changes:
> 1) Change suspend_save_csrs() and suspend_restore_csrs()
>    to public function as these functions are common to
>    suspend/hibernation. (patch 1)
> 2) Refactor the common code in the __cpu_resume_enter() function and
>    __hibernate_cpu_resume() function. The common code are used by
>    hibernation and suspend. (patch 2)
> 3) Enhance kernel_page_present() function to support huge page. (patch 3)
> 4) Add arch/riscv low level functions to support
>    hibernation/suspend to disk. (patch 4)
> 
> The above patches are based on kernel v6.3-rc3 and are tested on
> StarFive VF2 SBC board and Qemu. 
> ACPI platform mode is not supported in this series.
>

I tested this on QEMU, but, FYI, I had to use a raw backing file for
the swap disk, rather than a qcow2 backing file, otherwise it didn't
resume. It's probably worth looking into why that is.

Thanks,
drew