Re: [Xen-devel] [PATCH v3] x86/altp2m: Add a subop for obtaining the mem access of a page

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.08.18 at 11:38, <apop@xxxxxxxxxxxxxxx> wrote:
> On Tue, Jul 31, 2018 at 05:37:30AM -0600, Jan Beulich wrote:
>> >>> On 25.07.18 at 13:16, <apop@xxxxxxxxxxxxxxx> wrote:
>> > --- a/xen/include/public/hvm/hvm_op.h
>> > +++ b/xen/include/public/hvm/hvm_op.h
>> > @@ -234,7 +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);
>> >  
>> > -struct xen_hvm_altp2m_set_mem_access {
>> > +struct xen_hvm_altp2m_mem_access {
>> >      /* view */
>> >      uint16_t view;
>> >      /* Memory type */
>> > @@ -243,8 +243,8 @@ struct xen_hvm_altp2m_set_mem_access {
>> >      /* gfn */
>> >      uint64_t gfn;
>> >  };
>> > -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);
>> > +typedef struct xen_hvm_altp2m_mem_access xen_hvm_altp2m_mem_access_t;
>> > +DEFINE_XEN_GUEST_HANDLE(xen_hvm_altp2m_mem_access_t);
>> >  
>> >  struct xen_hvm_altp2m_set_mem_access_multi {
>> >      /* view */
>> > @@ -296,6 +296,8 @@ struct xen_hvm_altp2m_op {
>> >  #define HVMOP_altp2m_change_gfn           8
>> >  /* Set access for an array of pages */
>> >  #define HVMOP_altp2m_set_mem_access_multi 9
>> > +/* Get the access of a page of memory from a certain view */
>> > +#define HVMOP_altp2m_get_mem_access       10
>> >      domid_t domain;
>> >      uint16_t pad1;
>> >      uint32_t pad2;
>> > @@ -303,7 +305,7 @@ struct xen_hvm_altp2m_op {
>> >          struct xen_hvm_altp2m_domain_state         domain_state;
>> >          struct xen_hvm_altp2m_vcpu_enable_notify   enable_notify;
>> >          struct xen_hvm_altp2m_view                 view;
>> > -        struct xen_hvm_altp2m_set_mem_access       set_mem_access;
>> > +        struct xen_hvm_altp2m_mem_access           mem_access;
>> >          struct xen_hvm_altp2m_change_gfn           change_gfn;
>> >          struct xen_hvm_altp2m_set_mem_access_multi set_mem_access_multi;
>> >          uint8_t pad[64];
>> 
>> This being exposed to guests, the interface has to be considered
>> stable imo, in which case you can't rename things like this. You'd
>> need __XEN_INTERFACE_VERSION__ dependent logic (just like is the
>> case further up in the file).
> 
> Right.  Sorry about that.  Maybe just having separate structs for
> get/set would be cleaner in this case, even though they would be
> similar.

Personally I'd prefer to avoid having two structures with identical
layout but different tags. But if others think differently, I'm not
meaning to stand in the way.

Jan



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