linux-kernel - Re: [PATCH v7 12/17] ARM64: ACPI: Check if it runs on Xen to enable or disable ACPI

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Date:	Tue, 29 Mar 2016 17:18:38 +0100
From:	Will Deacon <will.deacon@....com>
To:	Shannon Zhao <shannon.zhao@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org,
	stefano.stabellini@...rix.com, david.vrabel@...rix.com,
	devicetree@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org, catalin.marinas@....com,
	julien.grall@....com, peter.huangpeng@...wei.com,
	xen-devel@...ts.xen.org, zhaoshenglong@...wei.com,
	mark.rutland@....com
Subject: Re: [PATCH v7 12/17] ARM64: ACPI: Check if it runs on Xen to enable
 or disable ACPI

On Thu, Mar 24, 2016 at 10:44:31PM +0800, Shannon Zhao wrote:
> When it's a Xen domain0 booting with ACPI, it will supply a /chosen and
> a /hypervisor node in DT. So check if it needs to enable ACPI.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@...aro.org>
> Reviewed-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> Acked-by: Hanjun Guo <hanjun.guo@...aro.org>
> ---
>  arch/arm64/kernel/acpi.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index d1ce8e2..4e92be0 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -67,10 +67,13 @@ static int __init dt_scan_depth1_nodes(unsigned long node,
>  {
>  	/*
>  	 * Return 1 as soon as we encounter a node at depth 1 that is
> -	 * not the /chosen node.
> +	 * not the /chosen node, or /hypervisor node when running on Xen.
>  	 */
> -	if (depth == 1 && (strcmp(uname, "chosen") != 0))
> -		return 1;
> +	if (depth == 1 && (strcmp(uname, "chosen") != 0)) {
> +		if (!xen_initial_domain() || (strcmp(uname, "hypervisor") != 0))
> +			return 1;
> +	}

Hmm, but xen_initial_domain() is false when xen isn't being used at all,
so it feels to me like this is a bit too far-reaching and is basically
claiming the "/hypervisor" namespace for Xen. Couldn't it be renamed to
"xen,hypervisor" or something?

Mark, got any thoughts on this?

Will