[hyperv] Check for required features

Other hypervisors (e.g. KVM) may provide an unusable subset of the
Hyper-V features, and our attempts to use these non-existent features
cause the guest to reboot.

Fix by explicitly checking for the Hyper-V features that we use.

Reported-by: Ján ONDREJ (SAL) <ondrejj@salstar.sk>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86/drivers/hyperv/hyperv.c

 	uint32_t discard_ebx;
 	uint32_t discard_ecx;
 	uint32_t discard_edx;
+	uint32_t available;
+	uint32_t permissions;
 
 	/* Check for presence of a hypervisor (not necessarily Hyper-V) */
 	x86_features ( &features );
 		return -ENODEV;
 	}
 
+	/* Check that required features and privileges are available */
+	cpuid ( HV_CPUID_FEATURES, &available, &permissions, &discard_ecx,
+		&discard_edx );
+	if ( ! ( available & HV_FEATURES_AVAIL_HYPERCALL_MSR ) ) {
+		DBGC ( hv, "HV %p has no hypercall MSRs (features %08x:%08x)\n",
+		       hv, available, permissions );
+		return -ENODEV;
+	}
+	if ( ! ( available & HV_FEATURES_AVAIL_SYNIC_MSR ) ) {
+		DBGC ( hv, "HV %p has no SynIC MSRs (features %08x:%08x)\n",
+		       hv, available, permissions );
+		return -ENODEV;
+	}
+	if ( ! ( permissions & HV_FEATURES_PERM_POST_MESSAGES ) ) {
+		DBGC ( hv, "HV %p cannot post messages (features %08x:%08x)\n",
+		       hv, available, permissions );
+		return -EACCES;
+	}
+	if ( ! ( permissions & HV_FEATURES_PERM_SIGNAL_EVENTS ) ) {
+		DBGC ( hv, "HV %p cannot signal events (features %08x:%08x)",
+		       hv, available, permissions );
+		return -EACCES;
+	}
+
 	return 0;
 }
 

src/arch/x86/drivers/hyperv/hyperv.h

 /** Get hypervisor identification */
 #define HV_CPUID_HYPERVISOR_ID 0x40000002UL
 
+/** Get hypervisor features */
+#define HV_CPUID_FEATURES 0x40000003UL
+
+/** SynIC MSRs are available */
+#define HV_FEATURES_AVAIL_SYNIC_MSR 0x00000004UL
+
+/** Hypercall MSRs are available */
+#define HV_FEATURES_AVAIL_HYPERCALL_MSR 0x00000020UL
+
+/** Guest may post messages */
+#define HV_FEATURES_PERM_POST_MESSAGES 0x00000010UL
+
+/** Guest may signal events */
+#define HV_FEATURES_PERM_SIGNAL_EVENTS 0x00000020UL
+
 /** Guest OS identity MSR */
 #define HV_X64_MSR_GUEST_OS_ID 0x40000000UL