Re: [Xen-devel] [PATCH 06/25 v7] xen/arm: vpl011: Add a new domctl API to initialize vpl011

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.08.17 at 12:28, <bhupinder.thakur@xxxxxxxxxx> wrote:
> Hi Jan,
> 
> On 7 August 2017 at 14:44, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>>> Bhupinder Thakur <bhupinder.thakur@xxxxxxxxxx> 08/07/17 10:55 AM >>>
>>>@@ -1148,6 +1149,24 @@ struct xen_domctl_psr_cat_op {
>>>uint32_t target;    /* IN */
>>>uint64_t data;      /* IN/OUT */
>>>};
>>>+
>>>+struct xen_domctl_vuart_op {
>>>+#define XEN_DOMCTL_VUART_OP_INIT  0
>>>+        uint32_t cmd;           /* XEN_DOMCTL_VUART_OP_* */
>>>+        domid_t console_domid;  /* IN */
>>>+#define XEN_DOMCTL_VUART_TYPE_VPL011 0
>>>+        uint32_t type;          /* IN - type of vuart.
>>>+                                 *      Currently only vpl011 supported.
>>>+                                 */
>>>+        xen_pfn_t gfn;          /* IN - guest gfn to be used as a
>>>+                                 *      ring buffer.
>>>+                                 */
>>>+        evtchn_port_t evtchn;   /* OUT - remote port of the event
>>>+                                 *       channel used for sending
>>>+                                 *       ring buffer events.
>>>+                                 */
>>>+};
>>
>> Please try to limit the amount of padding needed and make all remaining
>> padding fields explicit. That should then also make obvious that using
>> xen_pfn_t in domctl.h is not a good idea (the existing uses are bogus too
>> afaict - in the getpageframeinfo3 case the handler deals with the differing
>> width between 32- and 64-bit callers, and the cacheflush one is fine right
>> now only because it's ARM-only).
> 
> Please correct me if I understood your comment wrongly.
> 
> I believe you are referring to re-ordering the fields in the above
> structure so that the structure size is minimised.

Yes.

> Should I use type as unsigned long instead of xen_pfn_t in this structure?

No, uint64_aligned_t is what you want.

Jan


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