On Mon, 12 Aug 2019, Julien Grall wrote:
> A branch in the success case can be avoided by inverting the branch
> condition. At the same time, remove a pointless comment as Xen can only
> run at Hypervisor Mode.
>
> Lastly, document the behavior and the main registers usage within the
> function.
>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
Already provided by reviewed-by last time
> ---
> Changes in v2:
> - Patch added
> ---
> xen/arch/arm/arm32/head.S | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 4285f76463..c7b4fe4cd4 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -206,6 +206,16 @@ secondary_switched:
> b launch
> ENDPROC(init_secondary)
>
> +/*
> + * Check if the CPU supports virtualization extensions and has been booted
> + * in Hypervisor mode.
> + *
> + * This function will never return when the CPU doesn't support
> + * virtualization extensions or is booted in another mode than
> + * Hypervisor mode.
> + *
> + * Clobbers r0 - r3
> + */
> check_cpu_mode:
> /* Check that this CPU has Hyp mode */
> mrc CP32(r0, ID_PFR1)
> @@ -220,15 +230,12 @@ check_cpu_mode:
> mrs r0, cpsr
> and r0, r0, #0x1f /* Mode is in the low 5 bits of CPSR */
> teq r0, #0x1a /* Hyp Mode? */
> - beq hyp
> + moveq pc, lr /* Yes, return */
>
> /* OK, we're boned. */
> PRINT("- Xen must be entered in NS Hyp mode -\r\n")
> PRINT("- Please update the bootloader -\r\n")
> b fail
> -
> -hyp: PRINT("- Xen starting in Hyp mode -\r\n")
> - mov pc, lr
> ENDPROC(check_cpu_mode)
>
> zero_bss:
> --
> 2.11.0
>
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