[s390x] Provide a mechanism for checking installed CPU facilities

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/s390x/core/facility.c

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2026 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * Installed facilities
+ *
+ */
+
+#include <string.h>
+#include <ipxe/facility.h>
+
+/**
+ * Check if facility is installed
+ *
+ * @v facility		Facility ID
+ * @ret is_installed	Facility is installed
+ */
+int facility_is_installed ( unsigned int facility ) {
+	struct s390x_facilities facilities;
+	register unsigned long max asm ( "0" );
+
+	/* Get installed facilities */
+	memset ( &facilities, 0, sizeof ( facilities ) );
+	max = ( ( sizeof ( facilities.mask ) /
+		  sizeof ( facilities.mask[0] ) ) - 1 );
+	__asm__ ( "stfle %0" : "=R" ( facilities ), "+r" ( max ) );
+	DBGC ( &facilities, "FACILITY %016llx:%016llx:%016llx:%016llx\n",
+	       facilities.mask[0], facilities.mask[1], facilities.mask[2],
+	       facilities.mask[3] );
+
+	return ( !! ( facilities.mask[ facility / 64 ] &
+		      ( 1UL << ( ~facility % 64 ) ) ) );
+}

src/arch/s390x/include/ipxe/facility.h

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+#ifndef _IPXE_FACILITY_H
+#define _IPXE_FACILITY_H
+
+/** @file
+ *
+ * Installed facilities
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** Installed facilities */
+struct s390x_facilities {
+	/** Bit mask of installed facilities */
+	uint64_t mask[4];
+};
+
+extern int facility_is_installed ( unsigned int facility );
+
+#endif /* _IPXE_FACILITY_H */