Re: [PATCH v5 13/20] x86/kexec: Mark relocate_kernel page as ROX instead of RWX

[Ning, Hongyu]

On 2024/12/5 23:05, David Woodhouse wrote:
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
>
> All writes to the page now happen before it gets marked as executable
> (or after it's already switched to the identmap page tables where it's
> OK to be RWX).
>
> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> ---
>   arch/x86/kernel/machine_kexec_64.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index c9fd60f8f806..9232ad1562c8 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -323,7 +323,7 @@ int machine_kexec_prepare(struct kimage *image)
>   
>   	__memcpy(control_page, __relocate_kernel_start, reloc_end - reloc_start);
>   
> -	set_memory_x((unsigned long)control_page, 1);
> +	set_memory_rox((unsigned long)control_page, 1);
>   
>   	return 0;
>   }
> @@ -333,6 +333,7 @@ void machine_kexec_cleanup(struct kimage *image)
>   	void *control_page = page_address(image->control_code_page);
>   
>   	set_memory_nx((unsigned long)control_page, 1);
> +	set_memory_rw((unsigned long)control_page, 1);
>   
>   	free_transition_pgtable(image);
>   }

Hi David,

I've hit some kdump/kexec regression issue for guest kernel in KVM/QEMU 
based VM and reported in https://bugzilla.kernel.org/show_bug.cgi?id=219592.

based on further git bisect, it seems to be related with this commit, 
would you help to take a look?