s390/mem_detect: introduce z/VM specific diag260 call

In the case when z/VM memory is defined with "define storage config"
command, SCLP storage info is not available. Utilize diag260 "storage
configuration" call, to get information about z/VM specific guest memory
definitions with potential memory holes.
Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/boot/mem_detect.c

@@ -71,6 +71,53 @@ static unsigned long get_mem_detect_end(void)
 	return 0;
 }
 
+static int __diag260(unsigned long rx1, unsigned long rx2)
+{
+	register unsigned long _rx1 asm("2") = rx1;
+	register unsigned long _rx2 asm("3") = rx2;
+	register unsigned long _ry asm("4") = 0x10; /* storage configuration */
+	int rc = -1;				    /* fail */
+	unsigned long reg1, reg2;
+	psw_t old = S390_lowcore.program_new_psw;
+
+	asm volatile(
+		"	epsw	%0,%1\n"
+		"	st	%0,%[psw_pgm]\n"
+		"	st	%1,%[psw_pgm]+4\n"
+		"	larl	%0,1f\n"
+		"	stg	%0,%[psw_pgm]+8\n"
+		"	diag	%[rx],%[ry],0x260\n"
+		"	ipm	%[rc]\n"
+		"	srl	%[rc],28\n"
+		"1:\n"
+		: "=&d" (reg1), "=&a" (reg2),
+		  [psw_pgm] "=Q" (S390_lowcore.program_new_psw),
+		  [rc] "+&d" (rc), [ry] "+d" (_ry)
+		: [rx] "d" (_rx1), "d" (_rx2)
+		: "cc", "memory");
+	S390_lowcore.program_new_psw = old;
+	return rc == 0 ? _ry : -1;
+}
+
+static int diag260(void)
+{
+	int rc, i;
+
+	struct {
+		unsigned long start;
+		unsigned long end;
+	} storage_extents[8] __aligned(16); /* VM supports up to 8 extends */
+
+	memset(storage_extents, 0, sizeof(storage_extents));
+	rc = __diag260((unsigned long)storage_extents, sizeof(storage_extents));
+	if (rc == -1)
+		return -1;
+
+	for (i = 0; i < min_t(int, rc, ARRAY_SIZE(storage_extents)); i++)
+		add_mem_detect_block(storage_extents[i].start, storage_extents[i].end + 1);
+	return 0;
+}
+
 static int tprot(unsigned long addr)
 {
 	unsigned long pgm_addr;
@@ -132,6 +179,11 @@ void detect_memory(void)
 		return;
 	}
 
+	if (!diag260()) {
+		mem_detect.info_source = MEM_DETECT_DIAG260;
+		return;
+	}
+
 	scan_memory(rzm);
 	mem_detect.info_source = MEM_DETECT_TPROT_LOOP;
 	if (!max_physmem_end)

arch/s390/include/asm/mem_detect.h

@@ -7,6 +7,7 @@
 enum mem_info_source {
 	MEM_DETECT_NONE = 0,
 	MEM_DETECT_SCLP_STOR_INFO,
+	MEM_DETECT_DIAG260,
 	MEM_DETECT_TPROT_LOOP
 };