Re: [PATCH v8 1/6] tools/libxl: Check if fdt_{first, next}_subnode are present in libfdt

From: Julien Grall <julien.grall@citrix.com>
To: Ian Campbell <ian.campbell@citrix.com>,
	Julien Grall <julien.grall@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	Julien Grall <julien.grall@linaro.org>,
	tim@xen.org, stefano.stabellini@citrix.com,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v8 1/6] tools/libxl: Check if fdt_{first, next}_subnode are present in libfdt
Date: Wed, 13 May 2015 17:04:16 +0100	[thread overview]
Message-ID: <55537600.6020700@citrix.com> (raw)
In-Reply-To: <1431531541.8263.337.camel@citrix.com>

Hi Ian,

On 13/05/15 16:39, Ian Campbell wrote:
> On Wed, 2015-05-13 at 16:22 +0100, Julien Grall wrote:
> 
>> :(. Both the distribution are using an old version of libfdt where the 3
>> prototypes are defined but the implementation is not exposed in the
>> library (this is because they use a whitelist for building it)
>>
>> I gave look to see if we can import them from libfdt. It will require to
>> import few others in order to make them work:
>> 	- _fdt_check_node_offset
>> 	- _fdt_offset_ptr
>> 	- _nextprop
>>
>> I think we can skip the first one because it's only a validity check.
>> FWIW, we declared the the partial device tree should be trusted so valid.
>>
>> Nonetheless we would add 5 more functions (+ the actual 2) in libxl
>> which represents ~50 lines of codes.
>>
>> The 3 offending function have been correctly exposed since the version
>> v1.4.0 released in June 2013.
>>
>> I gave a look to major distribution to see which version is using an old
>> version of libfdt (i.e < 1.4.0:
>> 	- Centos: < Centos 6
>> 	- Debian: < Jessie => Wheezy using an old version
>> 	- Fedora: < Fedora 20
>> 	- openSuse: < opensuse 13.1
>> 	- ubuntu: < Ubuntu 14.04 => The LTS (14.04) is using a new version
>> 	- RedHat: < Redhat 6
>>
>> AFAICT, all major distributions except debian (for wheezy) are using a
>> libfdt > v1.4. So I would suggest to disable the partial device tree
>> support on distribution using older version.
> 
> OK, I think we can live with this.

I will resend the series later today or tomorrow.

>> If the user want to use platform device passthrough it would have either
>> to build a newer version of libfdt or append a device tree to the guest
>> kernel.
>>
>> Note: IIRC osstest is using wheezy. If so, we won't be able to test
>> platform device passthrough until the distribution version is upgraded.
>>
>> Although, we don't currently have a platform supporting non-PCI
>> passthrough in osstest.
> 
> Right, I'd expect us to have upgraded to Jessie before we got hold of
> such production hardware anyway.

Good!

Regards,

-- 
Julien Grall