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Re: [PATCH] xen/public: add comments regarding interface version bumps


  • To: Jürgen Groß <jgross@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Mon, 14 Oct 2024 13:36:19 +0200
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 14 Oct 2024 11:36:38 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 14.10.2024 13:01, Jürgen Groß wrote:
> On 14.10.24 12:48, Julien Grall wrote:
>> On 14/10/2024 11:33, Juergen Gross wrote:
>>> domctl.h and sysctl.h have an interface version, which needs to be
>>> bumped in case of incompatible modifications of the interface.
>>
>> What about vm_event.h?
> 
> Indeed.
> 
> There seem to be others missing, too. Here a git grep output of
> possible candidates (including domctl.h, sysctl.h and vm_event.h):
> 
> arch-x86/xen-mca.h:#define XEN_MCA_INTERFACE_VERSION 0x01ecc003
> domctl.h:#define XEN_DOMCTL_INTERFACE_VERSION 0x00000017
> hvm/hvm_op.h:#define HVMOP_ALTP2M_INTERFACE_VERSION 0x00000001
> platform.h:#define XENPF_INTERFACE_VERSION 0x03000001
> sysctl.h:#define XEN_SYSCTL_INTERFACE_VERSION 0x00000015
> vm_event.h:#define VM_EVENT_INTERFACE_VERSION 0x00000007
> xsm/flask_op.h:#define XEN_FLASK_INTERFACE_VERSION 1
> 
> I can add another patch for the missing ones (or 1 patch for each?)

Please don't. The situation is different there. Sysctl and domctl are
unstable interfaces, hence to change them in incompatible ways a bump
is all that's needed (in addition). That's quite different from cases
where the interface itself is stable. The only possible exception to
this is vm_event.h, which offers solely tools-only interfaces. I'm
not sure though whether "just" bumping the interface version there is
enough for an incompatible change to occur. Tamas?

Jan



 


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