s390: unify identity mapping limits handling

Currently we have to consider too many different values which
in the end only affect identity mapping size. These are:
1. max_physmem_end - end of physical memory online or standby.
   Always <= end of the last online memory block (get_mem_detect_end()).
2. CONFIG_MAX_PHYSMEM_BITS - the maximum size of physical memory the
   kernel is able to support.
3. "mem=" kernel command line option which limits physical memory usage.
4. OLDMEM_BASE which is a kdump memory limit when the kernel is executed as
   crash kernel.
5. "hsa" size which is a memory limit when the kernel is executed during
   zfcp/nvme dump.

Through out kernel startup and run we juggle all those values at once
but that does not bring any amusement, only confusion and complexity.

Unify all those values to a single one we should really care, that is
our identity mapping size.

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 44 insertions, 4 deletions

diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index eeda91fcf7cc..05f8eefa3dcf 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/string.h>
 #include <linux/elf.h>
+#include <asm/boot_data.h>
 #include <asm/sections.h>
 #include <asm/cpu_mf.h>
 #include <asm/setup.h>
@@ -14,6 +15,7 @@
 extern char __boot_data_start[], __boot_data_end[];
 extern char __boot_data_preserved_start[], __boot_data_preserved_end[];
 unsigned long __bootdata_preserved(__kaslr_offset);
+unsigned long __bootdata(ident_map_size);
 
 /*
  * Some code and data needs to stay below 2 GB, even when the kernel would be
@@ -128,6 +130,46 @@ static void handle_relocs(unsigned long offset)
 }
 
 /*
+ * Merge information from several sources into a single ident_map_size value.
+ * "ident_map_size" represents the upper limit of physical memory we may ever
+ * reach. It might not be all online memory, but also include standby (offline)
+ * memory. "ident_map_size" could be lower then actual standby or even online
+ * memory present, due to limiting factors. We should never go above this limit.
+ * It is the size of our identity mapping.
+ *
+ * Consider the following factors:
+ * 1. max_physmem_end - end of physical memory online or standby.
+ *    Always <= end of the last online memory block (get_mem_detect_end()).
+ * 2. CONFIG_MAX_PHYSMEM_BITS - the maximum size of physical memory the
+ *    kernel is able to support.
+ * 3. "mem=" kernel command line option which limits physical memory usage.
+ * 4. OLDMEM_BASE which is a kdump memory limit when the kernel is executed as
+ *    crash kernel.
+ * 5. "hsa" size which is a memory limit when the kernel is executed during
+ *    zfcp/nvme dump.
+ */
+static void setup_ident_map_size(unsigned long max_physmem_end)
+{
+	unsigned long hsa_size;
+
+	ident_map_size = max_physmem_end;
+	if (memory_limit)
+		ident_map_size = min(ident_map_size, memory_limit);
+	ident_map_size = min(ident_map_size, 1UL << MAX_PHYSMEM_BITS);
+
+#ifdef CONFIG_CRASH_DUMP
+	if (OLDMEM_BASE) {
+		kaslr_enabled = 0;
+		ident_map_size = min(ident_map_size, OLDMEM_SIZE);
+	} else if (ipl_block_valid && is_ipl_block_dump()) {
+		kaslr_enabled = 0;
+		if (!sclp_early_get_hsa_size(&hsa_size) && hsa_size)
+			ident_map_size = min(ident_map_size, hsa_size);
+	}
+#endif
+}
+
+/*
  * This function clears the BSS section of the decompressed Linux kernel and NOT the decompressor's.
  */
 static void clear_bss_section(void)
@@ -145,8 +187,7 @@ static void setup_vmalloc_size(void)
 
 	if (vmalloc_size_set)
 		return;
-	size = (memory_end ?: max_physmem_end) >> 3;
-	size = round_up(size, _SEGMENT_SIZE);
+	size = round_up(ident_map_size / 8, _SEGMENT_SIZE);
 	vmalloc_size = max(size, vmalloc_size);
 }
 
@@ -165,8 +206,7 @@ void startup_kernel(void)
 	sclp_early_read_info();
 	setup_boot_command_line();
 	parse_boot_command_line();
-	setup_memory_end();
-	detect_memory();
+	setup_ident_map_size(detect_memory());
 	setup_vmalloc_size();
 
 	random_lma = __kaslr_offset = 0;