Use CPUID flags to determine working components

This adds a few checks to make sure we're not trying to use features
that are not advertised with CPUID feature flags and avoid attaching
when Xen viridium emulation is turned on.

Prompted by a report from Kirill Miazine <km at krot ! org>, thanks!
Discussed with reyk@.

1 files changed, 9 insertions, 2 deletions

diff --git a/sys/dev/pv/hyperv.c b/sys/dev/pv/hyperv.c
index e3b6db5ed0e..1318d0011e3 100644
--- a/sys/dev/pv/hyperv.c
+++ b/sys/dev/pv/hyperv.c
@@ -263,7 +263,7 @@ hv_match(struct device *parent, void *match, void *aux)
 	struct pv_attach_args *pva = aux;
 	struct pvbus_hv *hv = &pva->pva_hv[PVBUS_HYPERV];
 
-	if (hv->hv_base == 0)
+	if ((hv->hv_major == 0 && hv->hv_minor == 0) || hv->hv_base == 0)
 		return (0);
 
 	return (1);
@@ -279,11 +279,18 @@ hv_attach(struct device *parent, struct device *self, void *aux)
 	sc->sc_pvbus = hv;
 	sc->sc_dmat = pva->pva_dmat;
 
+	if (!(hv->hv_features & CPUID_HV_MSR_HYPERCALL) ||
+	    !(hv->hv_features & CPUID_HV_MSR_SYNIC)) {
+		printf(": not functional\n");
+		return;
+	}
+
 	printf("\n");
 
 	hv_set_version(sc);
 
-	tc_init(&hv_timecounter);
+	if (hv->hv_features & CPUID_HV_MSR_TIME_REFCNT)
+		tc_init(&hv_timecounter);
 
 	if (hv_init_hypercall(sc))
 		return;