Re: [PATCH v6 04/15] x86/pvh: Use fixed_percpu_data for early boot GSBASE

[Borislav Petkov <bp@xxxxxxxxx>]

On Thu, Jan 23, 2025 at 02:07:36PM -0500, Brian Gerst wrote:
> Instead of having a private area for the stack canary, use
> fixed_percpu_data for GSBASE like the native kernel.
> 
> Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
> Reviewed-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
>  arch/x86/platform/pvh/head.S | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)

Use ./scripts/get_maintainer.pl pls. I've added Juergen now.

> diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
> index 4733a5f467b8..fa0072e0ca43 100644
> --- a/arch/x86/platform/pvh/head.S
> +++ b/arch/x86/platform/pvh/head.S
> @@ -173,10 +173,15 @@ SYM_CODE_START(pvh_start_xen)
>  1:
>       UNWIND_HINT_END_OF_STACK
>  
> -     /* Set base address in stack canary descriptor. */
> -     mov $MSR_GS_BASE,%ecx
> -     leal canary(%rip), %eax
> -     xor %edx, %edx
> +     /*
> +      * Set up GSBASE.
> +      * Note that, on SMP, the boot cpu uses init data section until
> +      * the per cpu areas are set up.

s/cpu/CPU/g

check your whole set pls.

> +      */
> +     movl $MSR_GS_BASE,%ecx
> +     leaq INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
> +     movq %edx, %eax
> +     shrq $32, %rdx
>       wrmsr