powerpc/fadump: consider f/w load area

OPAL loads kernel & initrd at 512MB offset (256MB size), also exported
as ibm,opal/dump/fw-load-area. So, if boot memory size of FADump is
less than 768MB, kernel memory to be exported as '/proc/vmcore' would
be overwritten by f/w while loading kernel & initrd. To avoid such a
scenario, enforce a minimum boot memory size of 768MB on OPAL platform
and skip using FADump if a newer F/W version loads kernel & initrd
above 768MB.

Also, irrespective of RMA size, set the minimum boot memory size
expected on pseries platform at 320MB. This is to avoid inflating the
minimum memory requirements on systems with 512M/1024M RMA size.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/156821381414.5656.1592867278535469652.stgit@hbathini.in.ibm.com

arch/powerpc/platforms/powernv/opal-fadump.c

@@ -9,6 +9,7 @@
 
 #include <linux/string.h>
 #include <linux/seq_file.h>
+#include <linux/of.h>
 #include <linux/of_fdt.h>
 #include <linux/libfdt.h>
 #include <linux/mm.h>
@@ -262,6 +263,11 @@ static int opal_fadump_setup_metadata(struct fw_dump *fadump_conf)
 	return err;
 }
 
+static u64 opal_fadump_get_bootmem_min(void)
+{
+	return OPAL_FADUMP_MIN_BOOT_MEM;
+}
+
 static int opal_fadump_register(struct fw_dump *fadump_conf)
 {
 	s64 rc = OPAL_PARAMETER;
@@ -606,6 +612,7 @@ static struct fadump_ops opal_fadump_ops = {
 	.fadump_init_mem_struct		= opal_fadump_init_mem_struct,
 	.fadump_get_metadata_size	= opal_fadump_get_metadata_size,
 	.fadump_setup_metadata		= opal_fadump_setup_metadata,
+	.fadump_get_bootmem_min		= opal_fadump_get_bootmem_min,
 	.fadump_register		= opal_fadump_register,
 	.fadump_unregister		= opal_fadump_unregister,
 	.fadump_invalidate		= opal_fadump_invalidate,
@@ -620,9 +627,9 @@ void __init opal_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node)
 	const __be32 *prop;
 	unsigned long dn;
 	u64 addr = 0;
+	int i, len;
 	s64 ret;
 
-
 	/*
 	 * Check if Firmware-Assisted Dump is supported. if yes, check
 	 * if dump has been initiated on last reboot.
@@ -638,6 +645,27 @@ void __init opal_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node)
 		return;
 	}
 
+	prop = of_get_flat_dt_prop(dn, "fw-load-area", &len);
+	if (prop) {
+		/*
+		 * Each f/w load area is an (address,size) pair,
+		 * 2 cells each, totalling 4 cells per range.
+		 */
+		for (i = 0; i < len / (sizeof(*prop) * 4); i++) {
+			u64 base, end;
+
+			base = of_read_number(prop + (i * 4) + 0, 2);
+			end = base;
+			end += of_read_number(prop + (i * 4) + 2, 2);
+			if (end > OPAL_FADUMP_MIN_BOOT_MEM) {
+				pr_err("F/W load area: 0x%llx-0x%llx\n",
+				       base, end);
+				pr_err("F/W version not supported!\n");
+				return;
+			}
+		}
+	}
+
 	fadump_conf->ops		= &opal_fadump_ops;
 	fadump_conf->fadump_supported	= 1;
 

arch/powerpc/platforms/powernv/opal-fadump.h

@@ -10,6 +10,13 @@
 
 #include <asm/reg.h>
 
+/*
+ * With kernel & initrd loaded at 512MB (with 256MB size), enforce a minimum
+ * boot memory size of 768MB to ensure f/w loading kernel and initrd doesn't
+ * mess with crash'ed kernel's memory during MPIPL.
+ */
+#define OPAL_FADUMP_MIN_BOOT_MEM		(0x30000000UL)
+
 /*
  * OPAL FADump metadata structure format version
  *

arch/powerpc/platforms/pseries/rtas-fadump.c

@@ -116,6 +116,11 @@ static u64 rtas_fadump_init_mem_struct(struct fw_dump *fadump_conf)
 	return addr;
 }
 
+static u64 rtas_fadump_get_bootmem_min(void)
+{
+	return RTAS_FADUMP_MIN_BOOT_MEM;
+}
+
 static int rtas_fadump_register(struct fw_dump *fadump_conf)
 {
 	unsigned int wait_time;
@@ -467,6 +472,7 @@ static void rtas_fadump_trigger(struct fadump_crash_info_header *fdh,
 
 static struct fadump_ops rtas_fadump_ops = {
 	.fadump_init_mem_struct		= rtas_fadump_init_mem_struct,
+	.fadump_get_bootmem_min		= rtas_fadump_get_bootmem_min,
 	.fadump_register		= rtas_fadump_register,
 	.fadump_unregister		= rtas_fadump_unregister,
 	.fadump_invalidate		= rtas_fadump_invalidate,

arch/powerpc/platforms/pseries/rtas-fadump.h

@@ -9,6 +9,15 @@
 #ifndef _PSERIES_RTAS_FADUMP_H
 #define _PSERIES_RTAS_FADUMP_H
 
+/*
+ * On some Power systems where RMO is 128MB, it still requires minimum of
+ * 256MB for kernel to boot successfully. When kdump infrastructure is
+ * configured to save vmcore over network, we run into OOM issue while
+ * loading modules related to network setup. Hence we need additional 64M
+ * of memory to avoid OOM issue.
+ */
+#define RTAS_FADUMP_MIN_BOOT_MEM	((0x1UL << 28) + (0x1UL << 26))
+
 /* Firmware provided dump sections */
 #define RTAS_FADUMP_CPU_STATE_DATA	0x0001
 #define RTAS_FADUMP_HPTE_REGION		0x0002