linux-kernel - Re: [PATCH fixes] riscv/purgatory: 4B align purgatory

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Message-ID: <c68ce83f-557e-4cf0-b72b-4424098e4afc@ghiti.fr>
Date: Fri, 28 Mar 2025 13:54:17 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Björn Töpel <bjorn@...nel.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, linux-riscv@...ts.infradead.org
Cc: Björn Töpel <bjorn@...osinc.com>,
 Daniel Maslowski <cyrevolt@...glemail.com>,
 Li Zhengyu <lizhengyu3@...wei.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH fixes] riscv/purgatory: 4B align purgatory_start

Hi Björn,

On 28/03/2025 09:53, Björn Töpel wrote:
> From: Björn Töpel <bjorn@...osinc.com>
>
> When a crashkernel is launched on RISC-V, the entry to purgatory is
> done by trapping via the stvec CSR. From riscv_kexec_norelocate():
>
>    |  ...
>    |  /*
>    |   * Switch to physical addressing
>    |   * This will also trigger a jump to CSR_STVEC
>    |   * which in this case is the address of the new
>    |   * kernel.
>    |   */
>    |  csrw    CSR_STVEC, a2
>    |  csrw    CSR_SATP, zero
>
> stvec requires that the address is 4B aligned, which was not the case,
> e.g.:
>
>    | Loaded purgatory at 0xffffc000
>    | kexec_file: kexec_file_load: type:1, start:0xffffd232 head:0x4 flags:0x6
>
> The address 0xffffd232 not 4B aligned.
>
> Correct by adding proper function alignment.
>
> With this change, crashkernels loaded with kexec-file will be able to
> properly enter the purgatory.
>
> Fixes: 736e30af583fb ("RISC-V: Add purgatory")
> Signed-off-by: Björn Töpel <bjorn@...osinc.com>
> ---
>   arch/riscv/purgatory/entry.S | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/arch/riscv/purgatory/entry.S b/arch/riscv/purgatory/entry.S
> index 0e6ca6d5ae4b..c5db2f072c34 100644
> --- a/arch/riscv/purgatory/entry.S
> +++ b/arch/riscv/purgatory/entry.S
> @@ -12,6 +12,7 @@
>   
>   .text
>   
> +.align	2
>   SYM_CODE_START(purgatory_start)
>   
>   	lla	sp, .Lstack
>
> base-commit: acb4f33713b9f6cadb6143f211714c343465411c


Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

Thanks,

Alex