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Re: [PATCH 1/7] xen/arm64: head: Don't set x22 and update the documentation
- To: Julien Grall <julien@xxxxxxx>
- From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- Date: Mon, 15 Aug 2022 13:43:27 +0000
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- Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Mon, 15 Aug 2022 13:43:49 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH 1/7] xen/arm64: head: Don't set x22 and update the documentation
Hi Julien,
> On 12 Aug 2022, at 20:24, Julien Grall <julien@xxxxxxx> wrote:
>
> From: Julien Grall <jgrall@xxxxxxxxxx>
>
> Since commit 7e14a47e7c73 ("xen/arm64: head Rework and document
> launch()"), the boot code is setting x22 but not read it.
>
> So remove the two instructions setting x22 and update the documentation
> to show x22 has no specific purpose.
>
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
Cheers
Bertrand
> ---
> xen/arch/arm/arm64/head.S | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 1babcc65d7c9..26cc7705f556 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -71,7 +71,7 @@
> * x19 - paddr(start)
> * x20 - phys offset
> * x21 - DTB address (boot cpu only)
> - * x22 - is_secondary_cpu
> + * x22 -
> * x23 - UART address
> * x24 -
> * x25 -
> @@ -305,8 +305,6 @@ real_start_efi:
> #endif
> PRINT("- Boot CPU booting -\r\n")
>
> - mov x22, #0 /* x22 := is_secondary_cpu */
> -
> bl check_cpu_mode
> bl cpu_init
> bl create_page_tables
> @@ -345,8 +343,6 @@ GLOBAL(init_secondary)
> adr x19, start /* x19 := paddr (start) */
> sub x20, x19, x0 /* x20 := phys-offset */
>
> - mov x22, #1 /* x22 := is_secondary_cpu */
> -
> mrs x0, mpidr_el1
> ldr x13, =(~MPIDR_HWID_MASK)
> bic x24, x0, x13 /* Mask out flags to get CPU ID */
> --
> 2.37.1
>
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