s390/mem_detect: move tprot loop to early boot phase

Move memory detection to early boot phase. To store online memory
regions "struct mem_detect_info" has been introduced together with
for_each_mem_detect_block iterator. mem_detect_info is later converted
to memblock.

Also introduces sclp_early_get_meminfo function to get maximum physical
memory and maximum increment number.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
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

@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <asm/sclp.h>
+#include <asm/sections.h>
+#include <asm/mem_detect.h>
+#include "compressed/decompressor.h"
+#include "boot.h"
+
+#define CHUNK_READ_WRITE 0
+#define CHUNK_READ_ONLY  1
+
+unsigned long __bootdata(max_physmem_end);
+struct mem_detect_info __bootdata(mem_detect);
+
+/* up to 256 storage elements, 1020 subincrements each */
+#define ENTRIES_EXTENDED_MAX						       \
+	(256 * (1020 / 2) * sizeof(struct mem_detect_block))
+
+/*
+ * To avoid corrupting old kernel memory during dump, find lowest memory
+ * chunk possible either right after the kernel end (decompressed kernel) or
+ * after initrd (if it is present and there is no hole between the kernel end
+ * and initrd)
+ */
+static void *mem_detect_alloc_extended(void)
+{
+	unsigned long offset = ALIGN(mem_safe_offset(), sizeof(u64));
+
+	if (IS_ENABLED(BLK_DEV_INITRD) && INITRD_START && INITRD_SIZE &&
+	    INITRD_START < offset + ENTRIES_EXTENDED_MAX)
+		offset = ALIGN(INITRD_START + INITRD_SIZE, sizeof(u64));
+
+	return (void *)offset;
+}
+
+static struct mem_detect_block *__get_mem_detect_block_ptr(u32 n)
+{
+	if (n < MEM_INLINED_ENTRIES)
+		return &mem_detect.entries[n];
+	if (unlikely(!mem_detect.entries_extended))
+		mem_detect.entries_extended = mem_detect_alloc_extended();
+	return &mem_detect.entries_extended[n - MEM_INLINED_ENTRIES];
+}
+
+/*
+ * sequential calls to add_mem_detect_block with adjacent memory areas
+ * are merged together into single memory block.
+ */
+void add_mem_detect_block(u64 start, u64 end)
+{
+	struct mem_detect_block *block;
+
+	if (mem_detect.count) {
+		block = __get_mem_detect_block_ptr(mem_detect.count - 1);
+		if (block->end == start) {
+			block->end = end;
+			return;
+		}
+	}
+
+	block = __get_mem_detect_block_ptr(mem_detect.count);
+	block->start = start;
+	block->end = end;
+	mem_detect.count++;
+}
+
+static unsigned long get_mem_detect_end(void)
+{
+	if (mem_detect.count)
+		return __get_mem_detect_block_ptr(mem_detect.count - 1)->end;
+	return 0;
+}
+
+static int tprot(unsigned long addr)
+{
+	unsigned long pgm_addr;
+	int rc = -EFAULT;
+	psw_t old = S390_lowcore.program_new_psw;
+
+	S390_lowcore.program_new_psw.mask = __extract_psw();
+	asm volatile(
+		"	larl	%[pgm_addr],1f\n"
+		"	stg	%[pgm_addr],%[psw_pgm_addr]\n"
+		"	tprot	0(%[addr]),0\n"
+		"	ipm	%[rc]\n"
+		"	srl	%[rc],28\n"
+		"1:\n"
+		: [pgm_addr] "=&d"(pgm_addr),
+		  [psw_pgm_addr] "=Q"(S390_lowcore.program_new_psw.addr),
+		  [rc] "+&d"(rc)
+		: [addr] "a"(addr)
+		: "cc", "memory");
+	S390_lowcore.program_new_psw = old;
+	return rc;
+}
+
+static void scan_memory(unsigned long rzm)
+{
+	unsigned long addr, size;
+	int type;
+
+	if (!rzm)
+		rzm = 1UL << 20;
+
+	addr = 0;
+	do {
+		size = 0;
+		/* assume lowcore is writable */
+		type = addr ? tprot(addr) : CHUNK_READ_WRITE;
+		do {
+			size += rzm;
+			if (max_physmem_end && addr + size >= max_physmem_end)
+				break;
+		} while (type == tprot(addr + size));
+		if (type == CHUNK_READ_WRITE || type == CHUNK_READ_ONLY) {
+			if (max_physmem_end && (addr + size > max_physmem_end))
+				size = max_physmem_end - addr;
+			add_mem_detect_block(addr, addr + size);
+		}
+		addr += size;
+	} while (addr < max_physmem_end);
+}
+
+void detect_memory(void)
+{
+	unsigned long rzm;
+
+	sclp_early_get_meminfo(&max_physmem_end, &rzm);
+	scan_memory(rzm);
+	mem_detect.info_source = MEM_DETECT_TPROT_LOOP;
+	if (!max_physmem_end)
+		max_physmem_end = get_mem_detect_end();
+}