Re: [Xen-devel] [PATCH] public/hvm: Export the HVM_PARAM_CALLBACK_VIA ABI in the API

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxx] On Behalf Of Jan Beulich
> Sent: 24 November 2015 07:33
> To: Andrew Cooper
> Cc: Keir (Xen.org); Ian Campbell; Tim (Xen.org); Ian Jackson; Xen-devel;
> Stefano Stabellini; Shannon Zhao
> Subject: Re: [Xen-devel] [PATCH] public/hvm: Export the
> HVM_PARAM_CALLBACK_VIA ABI in the API
> 
> >>> On 20.11.15 at 19:20, <andrew.cooper3@xxxxxxxxxx> wrote:
> > --- a/xen/include/public/hvm/params.h
> > +++ b/xen/include/public/hvm/params.h
> > @@ -29,18 +29,21 @@
> >   * Parameter space for HVMOP_{set,get}_param.
> >   */
> >
> > +#define HVM_PARAM_CALLBACK_IRQ 0
> > +
> >  /*
> >   * How should CPU0 event-channel notifications be delivered?
> > - * val[63:56] == 0: val[55:0] is a delivery GSI (Global System Interrupt).
> > - * val[63:56] == 1: val[55:0] is a delivery PCI INTx line, as follows:
> > - *                  Domain = val[47:32], Bus  = val[31:16],
> > - *                  DevFn  = val[15: 8], IntX = val[ 1: 0]
> > - * val[63:56] == 2: val[7:0] is a vector number, check for
> > - *                  XENFEAT_hvm_callback_vector to know if this delivery
> > - *                  method is available.
> > + *
> >   * If val == 0 then CPU0 event-channel notifications are not delivered.
> > + * If val != 0, val[63:56] encodes the type, as follows:
> >   */
> > -#define HVM_PARAM_CALLBACK_IRQ 0
> > +#define HVM_PARAM_CALLBACK_TYPE_GSI      0 /* val[55:0] is a delivery
> GSI */
> > +#define HVM_PARAM_CALLBACK_TYPE_PCI_INTX 1 /* val[55:0] is a
> delivery PCI INTx line:
> > +                                              Domain = val[47:32], Bus  = 
> > val[31:16],
> > +                                              DevFn  = val[15: 8], IntX = 
> > val[ 1: 0] */
> > +#define HVM_PARAM_CALLBACK_TYPE_VECTOR   2 /* val[7:0] is a vector
> number, check for
> > +                                              XENFEAT_hvm_callback_vector 
> > to know if
> > +                                              this delivery method is 
> > available. */
> 
> Would you not think that while cleaning this up, doing some
> re-formatting would also help? I.e. Putting the comments on lines of
> their own instead of at the end (even more deeply indented than
> they were before)? Also the first two of these last three comments
> are missing full stops.
> 
> Also considering
> 
>  * Attempting to use GSI 0 will actually disable callbacks
> 
> in your patch comments, I'd suggest extending the GSI comment to
> state that it has to be a non-zero one.
> 

Could we also perhaps deprecate this whole mechanism at this point? I added 
HVMOP_set_evtchn_upcall_vector quite a while ago now.

  Paul

> Jan
> 
> 
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