Re: [Qemu-devel] [PATCH v2] Import Linux headers for KVM and vhost

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-05-03 19:32, Edgar E. Iglesias wrote:
> On Tue, May 03, 2011 at 08:13:04PM +0300, Avi Kivity wrote:
>> On 05/03/2011 08:09 PM, Jan Kiszka wrote:
>>>>
>>>>  Reluctant ack.
>>>
>>> What downsides do you see?
>>
>> The usual "it shouldn't be this way".  Every other package (including, I 
>> think, glibc) uses the sanitized system headers.  Except for kvm-kmod, 
>> the system headers are always available.
> 
> I agree, it doesn't feel quite right to bring in the headers. I don't have
> any alternative suggestions (besides better HOWTOs/Documentation) though. 

Again, the downside of the current approach are:
 - outdated distro headers silently disable features during build time
   (happened to me with vhost e.g.)
 - build breakages against older kernels / headers are pre-programmed
   as hardly anyone tests all the possible combinations
 - tons of #ifdef in the code + configure checks to catch the possible
   combinations

Also note that [1] recommends this approach as well. I'm not aware of
good examples, but I would be fairly surprised if we were the first to
do this.

Jan

[1] http://kernelnewbies.org/KernelHeaders

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