Re: [Xen-devel] [PATCH 3/8] xen/arm: acpi: Don't fallback on DT when user request ACPI

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 3 Feb 2017, Julien Grall wrote:
> On ARM, when the user put 'acpi=force' Xen will use ACPI over DT.
> Currently, if Xen fails to initialize ACPI it will fallback on DT.
> 
> This behavior makes difficult for a user to notice Xen didn't used ACPI
> has requested on platform where the firmware is providing both ACPI and DT.
> 
> Rather than fallback on DT during a failure, panic when 'acpi=force'.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> 
> ---
>     I am wondering if we should do the same with acpi=on. So a user
>     would notice directly if something went wrong with ACPI.
>     Otherwise you would boot up to the prompt and barely notice that DT
>     was used.

I would keep the current behavior as is and add new parameter that means
"acpi and only acpi". Today acpi=force means "acpi is preferred to
device tree". It doesn't mean that if acpi fail, Xen should panic.

Maybe acpi=strict or acpi=mandatory?


> ---
>  xen/arch/arm/acpi/boot.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/xen/arch/arm/acpi/boot.c b/xen/arch/arm/acpi/boot.c
> index 889208a..65ef632 100644
> --- a/xen/arch/arm/acpi/boot.c
> +++ b/xen/arch/arm/acpi/boot.c
> @@ -272,6 +272,11 @@ int __init acpi_boot_table_init(void)
>      return 0;
>  
>  disable:
> +
> +    /* Panic if the user has requested ACPI but Xen is able to initialize. */
> +    if ( param_acpi_force )
> +        panic("Unable to use ACPI");
> +
>      disable_acpi();
>  
>      return error;
> -- 
> 1.9.1
> 

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