Re: [licensing] was: [XTF PATCH 04/16] vvmx: add C wrappers of vmxon/vmread/vmptrld

From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Haozhong Zhang <haozhong.zhang@intel.com>
Cc: xen-devel@lists.xenproject.org, Kevin Tian <kevin.tian@intel.com>,
	Ian Jackson <Ian.Jackson@eu.citrix.com>,
	Lars Kurth <lars.kurth@citrix.com>
Subject: Re: [licensing] was: [XTF PATCH 04/16] vvmx: add C wrappers of vmxon/vmread/vmptrld
Date: Mon, 19 Dec 2016 15:58:28 +0000	[thread overview]
Message-ID: <e53c38b8-af95-c4c7-8478-a8f4c87d09ff@citrix.com> (raw)
In-Reply-To: <20161219032036.4iq3ijyeo5mgbqam@hz-desktop>

On 19/12/16 03:20, Haozhong Zhang wrote:
> On 12/16/16 19:03 +0000, Andrew Cooper wrote:
>> On 16/12/16 13:43, Haozhong Zhang wrote:
>>> diff --git a/include/arch/x86/hvm/vmx/vmcs.h
>>> b/include/arch/x86/hvm/vmx/vmcs.h
>>> new file mode 100644
>>> index 0000000..e1a6ef8
>>> --- /dev/null
>>> +++ b/include/arch/x86/hvm/vmx/vmcs.h
>>> @@ -0,0 +1,179 @@
>>> +#ifndef XTF_X86_HVM_VMX_VMCS_H
>>> +#define XTF_X86_HVM_VMX_VMCS_H
>>> +
>>> +/* VMCS field encodings. */
>>> +#define VMCS_HIGH(x) ((x) | 1)
>>> +enum vmcs_field {
>>> +    VIRTUAL_PROCESSOR_ID            = 0x00000000,
>>> +    POSTED_INTR_NOTIFICATION_VECTOR = 0x00000002,
>>> +    EPTP_INDEX                      = 0x00000004,
>>> +#define GUEST_SEG_SELECTOR(sel) (GUEST_ES_SELECTOR + (sel) * 2) /*
>>> ES ... GS */
>>
>> Unfortunately, there is probably a BSD/GPL licensing issue here.
>>
>> XTF is BSD clause 2 licensed, because a lot of the core microkernel bits
>> are generally useful to other microkernel projects, and I have specific
>> plans to contribute improvements back to the likes of Mini-OS and
>> HVMLoader.  I would specifically like to maintain this property.
>>
>> Xen, following its Linux heritage, is strictly GPLv2 (other than the
>> public headers, which are specifically different).
>>
>>
>> Having XTF use the same naming as Xen is convenient for development, and
>> I specifically don't want to get caught up in tricks like renaming
>> constants;
>
> but renaming or taking names from other BSD-licensed projects [1] could
> keep the whole project as purely BSD-licensed.

That would also work.

I also tend to only pull in defines which are actually used, but that is
just personal choice and to keep the size of the commits down.

>
> [1]
> https://github.com/freebsd/freebsd/blob/master/sys/amd64/vmm/intel/vmcs.h
>
>> these names inherit from the architecture manual and calling
>> them anything else would be even worse. If we were to go down this
>> route, being able to keep the header file in sync would be useful, but
>> dual licensing it Xen would be complicated and confusing.
>>
>> BSD and GPL are compatible licenses.  One option Ian suggested would be
>> to have a GPL subdirectory in XTF which clearly separates GPL content
>> from BSD content.  The resulting tests would become GPL, but the primary
>> distribution method is "git clone && make", so there are no issues
>> there.
>
> If I want to use the BSD-licensed files individually in other
> projects, will I need to keep a GPL license with them?

Only if the GPL file needed to be ported as well.  In this case, it is
only the VMX test which uses it, rather than any of the core code.

I don't plan on porting entire files to other projects, but individual
functions certainly.  (Having said that, I do plan on moving the entire
vsnprintf() implementation to hvmloader so it can actually format 64bit
integers).

~Andrew

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