linux-kernel - Re: [PATCH v2 2/8] riscv: don't export va_kernel_pa

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Message-ID: <825ab2df-c040-4454-9db6-8d08bc3df592@ghiti.fr>
Date: Fri, 21 Jun 2024 12:27:43 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Nam Cao <namcao@...utronix.de>, Alexandre Ghiti <alexghiti@...osinc.com>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/8] riscv: don't export va_kernel_pa_offset in
 vmcoreinfo for XIP kernel

Hi Nam,

On 07/06/2024 22:22, Nam Cao wrote:
> The crash utility uses va_kernel_pa_offset to translate virtual addresses.
> This is incorrect in the case of XIP kernel, because va_kernel_pa_offset is
> not the virtual-physical address offset (yes, the name is misleading; this
> variable will be removed for XIP in a following commit).
>
> Stop exporting this variable for XIP kernel. The replacement is to be
> determined, note it as a TODO for now.
>
> Signed-off-by: Nam Cao <namcao@...utronix.de>
> ---
>   arch/riscv/kernel/vmcore_info.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/arch/riscv/kernel/vmcore_info.c b/arch/riscv/kernel/vmcore_info.c
> index 6d7a22522d63..d5e448aa90e7 100644
> --- a/arch/riscv/kernel/vmcore_info.c
> +++ b/arch/riscv/kernel/vmcore_info.c
> @@ -19,6 +19,13 @@ void arch_crash_save_vmcoreinfo(void)
>   #endif
>   #endif
>   	vmcoreinfo_append_str("NUMBER(KERNEL_LINK_ADDR)=0x%lx\n", KERNEL_LINK_ADDR);
> +#ifdef CONFIG_XIP_KERNEL
> +	/* TODO: Communicate with crash-utility developers on the information to
> +	 * export. The XIP case is more complicated, because the virtual-physical
> +	 * address offset depends on whether the address is in ROM or in RAM.
> +	 */
> +#else
>   	vmcoreinfo_append_str("NUMBER(va_kernel_pa_offset)=0x%lx\n",
>   						kernel_map.va_kernel_pa_offset);
> +#endif
>   }


So that will regress crash on XIP kernels, but on the other hand this 
was wrong in the first place. And not sure anyone ever used crash on a 
XIP platform.

At least people will know that using va_kernel_pa_offset was wrong, so:

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

Thanks for all your changes in v2,

Alex