Re: [Xen-devel] [PATCH v4] x86/altp2m: Add a subop for obtaining the mem access of a page

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.09.18 at 16:44, <wei.liu2@xxxxxxxxxx> wrote:
> On Mon, Sep 03, 2018 at 06:47:34PM +0300, Adrian Pop wrote:
>> --- a/xen/include/public/hvm/hvm_op.h
>> +++ b/xen/include/public/hvm/hvm_op.h
>> @@ -234,6 +234,7 @@ struct xen_hvm_altp2m_view {
>>  typedef struct xen_hvm_altp2m_view xen_hvm_altp2m_view_t;
>>  DEFINE_XEN_GUEST_HANDLE(xen_hvm_altp2m_view_t);
>>  
>> +#if __XEN_INTERFACE_VERSION__ < 0x00040a00
>>  struct xen_hvm_altp2m_set_mem_access {
>>      /* view */
>>      uint16_t view;
>> @@ -245,6 +246,19 @@ struct xen_hvm_altp2m_set_mem_access {
>>  };
>>  typedef struct xen_hvm_altp2m_set_mem_access 
>> xen_hvm_altp2m_set_mem_access_t;
>>  DEFINE_XEN_GUEST_HANDLE(xen_hvm_altp2m_set_mem_access_t);
>> +#endif /* __XEN_INTERFACE_VERSION__ < 0x00040a00 */
> 
> #else here please, otherwise you're adding this new interface to a set
> of old interfaces.

I don't think we do so elsewhere, so I'd prefer if we didn't do so
here either. By unconditionally exposing the new interface we
allow people to morph their code in steps, rather than all in one
go at the point they bump their __XEN_INTERFACE_VERSION__
setting.

Jan



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