[PATCH] Load crash kernel high on x86

[Petr Tesarik]

Hello,

There may be more than one crash kernel regions on x86. However, the kexec
syscall checks that target address is within crashk_res boundaries. Looking
at the logic in arch/x86/kernel/setup.c, there are only two possible layouts:

  1. crashk_res is below 4G, and there is only one region,
  2. crashk_res is above 4G, and crashk_low_res is below 4G

In either case, kexec-tools must pick the highest region.

Currently, kexec-tools picks the largest region. If high reservation is
smaller than low, kexec(2) returns -EADDRNOTAVAIL, and kexec prints out
this error message:

kexec_load failed: Cannot assign requested address

Signed-off-by: Petr Tesarik <ptesarik at suse.com>
---
 kexec/arch/i386/crashdump-x86.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c
index 63959b7..2710a9e 100644
--- a/kexec/arch/i386/crashdump-x86.c
+++ b/kexec/arch/i386/crashdump-x86.c
@@ -1034,16 +1034,8 @@ int get_max_crash_kernel_limit(uint64_t *start, uint64_t *end)
 	if (!crash_reserved_mem_nr)
 		return -1;
 
-	for (i = crash_reserved_mem_nr - 1; i >= 0; i--) {
-		sz = crash_reserved_mem[i].end - crash_reserved_mem[i].start +1;
-		if (sz <= sz_max)
-			continue;
-		sz_max = sz;
-		idx = i;
-	}
-
-	*start = crash_reserved_mem[idx].start;
-	*end = crash_reserved_mem[idx].end;
+	*start = crash_reserved_mem[crash_reserved_mem_nr - 1].start;
+	*end = crash_reserved_mem[crash_reserved_mem_nr - 1].end;
 
 	return 0;
 }
-- 
2.1.4