port-xen/58362: xen_rtc_set fails to zero-initialize XENPF_settime(64) command

[campbell+netbsd%mumble.net@localhost]

>Number:         58362
>Category:       port-xen
>Synopsis:       xen_rtc_set fails to zero-initialize XENPF_settime(64) command
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-xen-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jun 23 20:40:00 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current, 10, 9, ...
>Organization:
The XenBSD Clockdationroot:/bin/sh
>Environment:
>Description:
   1092 static int
   1093 xen_rtc_set(struct todr_chip_handle *todr, struct timeval *tvp)
   1094 {
...
   1097 	xen_platform_op_t op;
...
   1108 		/* Set the hypervisor wall clock time.  */
   1109 		op.cmd = XENPF_settime;
   1110 		op.u.settime.secs = tvp->tv_sec;
   1111 		op.u.settime.nsecs = tvp->tv_usec * 1000;
   1112 		op.u.settime.system_time = systime_ns;
   1113 		return HYPERVISOR_platform_op(&op);

https://nxr.netbsd.org/xref/src/sys/arch/xen/xen/xen_clock.c?r=1.18#1092

But for newer Xen interfaces, there is an extra member called `mbz' in XENPF_settime's argument:

#define XENPF_settime64           62
struct xenpf_settime64 {
    /* IN variables. */
    uint64_t secs;
    uint32_t nsecs;
    uint32_t mbz;
    uint64_t system_time;
};
#if __XEN_INTERFACE_VERSION__ < 0x00040600
#define XENPF_settime XENPF_settime32
#define xenpf_settime xenpf_settime32
#else
#define XENPF_settime XENPF_settime64
#define xenpf_settime xenpf_settime64
#endif

And Xen itself enforces this:

 221     case XENPF_settime64:
 222         if ( likely(!op->u.settime64.mbz) )
 223             do_settime(op->u.settime64.secs,
 224                        op->u.settime64.nsecs,
 225                        op->u.settime64.system_time);
 226         else
 227             ret = -EINVAL;
 228         break;

https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/x86/platform_hypercall.c;h=23fadbc782273c8111d2938aa9618360f908573c;hb=543bbddf79f105682904c3b5a09c5a1692ae4b15#l221
>How-To-Repeat:
code inspection
>Fix:
memset(&op, 0, sizeof(op));