linux-kernel - Re: [Xen-devel] [PATCH v2 14/16] Xen: EFI: Parse DT parameters for Xen specific UEFI

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Message-ID: <569E3E18.2040003@linaro.org>
Date:	Tue, 19 Jan 2016 21:46:00 +0800
From:	Shannon Zhao <shannon.zhao@...aro.org>
To:	Mark Rutland <mark.rutland@....com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Shannon Zhao <zhaoshenglong@...wei.com>,
	linux-arm-kernel@...ts.infradead.org, ard.biesheuvel@...aro.org,
	stefano.stabellini@...rix.com, david.vrabel@...rix.com,
	devicetree@...r.kernel.org, linux-efi@...r.kernel.org,
	catalin.marinas@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, xen-devel@...ts.xen.org,
	julien.grall@...rix.com, peter.huangpeng@...wei.com,
	matt@...eblueprint.co.uk
Subject: Re: [Xen-devel] [PATCH v2 14/16] Xen: EFI: Parse DT parameters for
 Xen specific UEFI



On 2016/1/19 21:43, Mark Rutland wrote:
> On Tue, Jan 19, 2016 at 09:19:05PM +0800, Shannon Zhao wrote:
>>
>>
>> On 2016/1/18 23:41, Stefano Stabellini wrote:
>>> CC'ing Matt Fleming
>>>
>>> On Fri, 15 Jan 2016, Shannon Zhao wrote:
>>>> From: Shannon Zhao <shannon.zhao@...aro.org>
>>>> @@ -520,15 +531,28 @@ static int __init fdt_find_uefi_params(unsigned long node, const char *uname,
>>>>   				       int depth, void *data)
>>>>   {
>>>>   	struct param_info *info = data;
>>>> +	struct params *dt_params;
>>>> +	unsigned int size;
>>>>   	const void *prop;
>>>>   	void *dest;
>>>>   	u64 val;
>>>>   	int i, len;
>>>>
>>>> -	if (depth != 1 || strcmp(uname, "chosen") != 0)
>>>> -		return 0;
>>>> +	if (efi_enabled(EFI_PARAVIRT)) {
>>>> +		if (depth != 2 || strcmp(uname, "uefi") != 0)
>>>
>>> You are already introducing this check in the previous patch when
>>> setting EFI_PARAVIRT, why do this again now?  But if we need to do this
>>> check again, then, like Mark suggested, it should be done against the
>>> full path.
>>>
>> This check just wants to confirm that the current node is the "uefi"
>> node and we can parse it with xen_fdt_params now.
>
> There is no single "uefi" node as many nodes can share that name. There
> is at most a single, /hypervisor/uefi node, as that is qualified by a
> full path.
>
Sure, I will check it by full path.

> Checking the leaf node name, as above, is insufficient. For example, the
> below will be accepted:
>
> * /chosen/uefi
> * /foo/uefi
> * /not-a-hypervisor/uefi
>
> Any of these could exist in addition to a /hypervisor/uefi node, and
> could appear ealier or later in the DTB.
>
> There may be reasons to add such nodes in future, and regardless we
> should not read properties from an invalid/wrong node.
>
> Thanks,
> Mark.
>

-- 
Shannon