[PATCH 2/2] kexec: Respect memory limit while building crash memory ranges on ppc64

[mahesh@xxxxxxxxxxxxxxxxxx (Mahesh J Salgaonkar)]

From: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>

Fix it on ppc64 also. This patch now reads the memory limit information
from device-tree file and limits the crash memory ranges accordingly.

Tested this patch on ppc64 with a kernel patch by Suzuki.

Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
---
 kexec/arch/ppc64/crashdump-ppc64.c |   11 ++++++++++-
 kexec/arch/ppc64/crashdump-ppc64.h |    1 +
 kexec/arch/ppc64/kexec-ppc64.c     |   28 ++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 1 deletions(-)

diff --git a/kexec/arch/ppc64/crashdump-ppc64.c b/kexec/arch/ppc64/crashdump-ppc64.c
index 30ef443..690b1f7 100644
--- a/kexec/arch/ppc64/crashdump-ppc64.c
+++ b/kexec/arch/ppc64/crashdump-ppc64.c
@@ -84,10 +84,19 @@ static unsigned long long cstart, cend;
 static int memory_ranges;
 
 /*
- * Exclude the region that lies within crashkernel
+ * Exclude the region that lies within crashkernel and above the memory
+ * limit which is reflected by mem= kernel option.
  */
 static void exclude_crash_region(uint64_t start, uint64_t end)
 {
+	/* If memory_limit is set then exclude the memory region above it. */
+	if (memory_limit) {
+		if (start > memory_limit)
+			return;
+		if (end > memory_limit)
+			end = memory_limit;
+	}
+
 	if (cstart < end && cend > start) {
 		if (start < cstart && end > cend) {
 			crash_memory_range[memory_ranges].start = start;
diff --git a/kexec/arch/ppc64/crashdump-ppc64.h b/kexec/arch/ppc64/crashdump-ppc64.h
index be02213..739c61f 100644
--- a/kexec/arch/ppc64/crashdump-ppc64.h
+++ b/kexec/arch/ppc64/crashdump-ppc64.h
@@ -27,6 +27,7 @@ void add_usable_mem_rgns(unsigned long long base, unsigned long long size);
 
 extern uint64_t crash_base;
 extern uint64_t crash_size;
+extern uint64_t memory_limit;
 extern unsigned int rtas_base;
 extern unsigned int rtas_size;
 
diff --git a/kexec/arch/ppc64/kexec-ppc64.c b/kexec/arch/ppc64/kexec-ppc64.c
index 2f12907..189d48e 100644
--- a/kexec/arch/ppc64/kexec-ppc64.c
+++ b/kexec/arch/ppc64/kexec-ppc64.c
@@ -39,6 +39,7 @@ static struct memory_range *memory_range = NULL;
 static struct memory_range *base_memory_range = NULL;
 static uint64_t rmo_top;
 uint64_t memory_max = 0;
+uint64_t memory_limit = 0;
 static int nr_memory_ranges, nr_exclude_ranges;
 uint64_t crash_base, crash_size;
 unsigned int rtas_base, rtas_size;
@@ -408,6 +409,33 @@ static int get_devtree_details(unsigned long kexec_flags)
 				add_usable_mem_rgns(0, crash_base + crash_size);
 				reserve(KDUMP_BACKUP_LIMIT, crash_base-KDUMP_BACKUP_LIMIT);
 			}
+			/*
+			 * Read the first kernel's memory limit.
+			 * If the first kernel is booted with mem= option then
+			 * it would export "linux,memory-limit" file
+			 * reflecting value for the same.
+			 */
+			memset(fname, 0, sizeof(fname));
+			strcpy(fname, device_tree);
+			strcat(fname, dentry->d_name);
+			strcat(fname, "/linux,memory-limit");
+			if ((file = fopen(fname, "r")) == NULL) {
+				if (errno != ENOENT) {
+					perror(fname);
+					goto error_opencdir;
+                                }
+				errno = 0;
+				/*
+				 * File not present.
+				 * fall through. On older kernel this file
+				 * is not present.
+				 */
+			}
+			else if (fread(&memory_limit, sizeof(uint64_t), 1, file)
+								!= 1) {
+				perror(fname);
+				goto error_openfile;
+			}
 
 			memset(fname, 0, sizeof(fname));
 			strcpy(fname, device_tree);