Re: [PATCH 7/7] x86/kexec: Zero general purpose registers

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/06/2026 4:45 pm, Kevin Lampis wrote:
> Purgatory zeros these general purpose registers before jumping to the
> new kernel. When doing kexec on an EFI kernel there is no purgatory so
> we need to zero the registers here instead. This change shouldn't affect
> the functionality of legacy kexec.
>
> Signed-off-by: Kevin Lampis <klampis@xxxxxxxxxx>

The subject wants to be "x86/kexec: Zero GPRs before entering new
kernel" or similar.

> diff --git a/xen/arch/x86/x86_64/kexec_reloc.S 
> b/xen/arch/x86/x86_64/kexec_reloc.S
> index 6a2c839b83..be9e487f7a 100644
> --- a/xen/arch/x86/x86_64/kexec_reloc.S
> +++ b/xen/arch/x86/x86_64/kexec_reloc.S
> @@ -94,6 +108,13 @@ FUNC(kexec_reloc, PAGE_SIZE)
>          lea     compatibility_mode(%rip), %rax
>          push    $0x10
>          push    %rax
> +
> +        xor %edi, %edi
> +        xor %eax, %eax
> +        xor %ebx, %ebx
> +        xor %ecx, %ecx
> +        xor %edx, %edx
> +
>          lretq
>  END(kexec_reloc)
>  

This hunk is in the wrong place.  It wants to be lower down at the end
of compatibility_mode, where there's another /* Jump to the image entry
point */ comment.

~Andrew