[PATCH v2] x86/crash: Update the stale comment in reserve_crashkernel()

[Xunlei Pang]

CRASH_KERNEL_ADDR_MAX has been missing for a long time,
update it with more detailed explanation.

Cc: Robert LeBlanc <***@leblancnet.us>
Cc: Baoquan He <***@redhat.com>
Signed-off-by: Xunlei Pang <***@redhat.com>
---
arch/x86/kernel/setup.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 4cfba94..c32a167 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -575,7 +575,9 @@ static void __init reserve_crashkernel(void)
/* 0 means: find the address automatically */
if (crash_base <= 0) {
/*
- * kexec want bzImage is below CRASH_KERNEL_ADDR_MAX
+ * Set CRASH_ADDR_LOW_MAX upper bound for crash memory
+ * as old kexec-tools loads bzImage below that, unless
+ * "crashkernel=size[KMG],high" is specified.
*/
crash_base = memblock_find_in_range(CRASH_ALIGN,
high ? CRASH_ADDR_HIGH_MAX

[Dave Young]

Hi, Xunlei

Post by Xunlei Pang
CRASH_KERNEL_ADDR_MAX has been missing for a long time,
update it with more detailed explanation.
---
arch/x86/kernel/setup.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 4cfba94..c32a167 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -575,7 +575,9 @@ static void __init reserve_crashkernel(void)
/* 0 means: find the address automatically */
if (crash_base <= 0) {
/*
- * kexec want bzImage is below CRASH_KERNEL_ADDR_MAX
+ * Set CRASH_ADDR_LOW_MAX upper bound for crash memory
+ * as old kexec-tools loads bzImage below that, unless
+ * "crashkernel=size[KMG],high" is specified.

There is already comment before the define of those macros, also
there are 32bit case which has a different reason about 512M there as
well.

So it looks better to just drop the one line comment without adding
further comments here.

Post by Xunlei Pang
*/
crash_base = memblock_find_in_range(CRASH_ALIGN,
high ? CRASH_ADDR_HIGH_MAX
--
1.8.3.1

Thanks
Dave

[Xunlei Pang]

Post by Dave Young
Hi, Xunlei

Post by Xunlei Pang
CRASH_KERNEL_ADDR_MAX has been missing for a long time,
update it with more detailed explanation.
---
arch/x86/kernel/setup.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 4cfba94..c32a167 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -575,7 +575,9 @@ static void __init reserve_crashkernel(void)
/* 0 means: find the address automatically */
if (crash_base <= 0) {
/*
- * kexec want bzImage is below CRASH_KERNEL_ADDR_MAX
+ * Set CRASH_ADDR_LOW_MAX upper bound for crash memory
+ * as old kexec-tools loads bzImage below that, unless
+ * "crashkernel=size[KMG],high" is specified.

There is already comment before the define of those macros, also
there are 32bit case which has a different reason about 512M there as
well.

If we see from the kexec's perspective, we have a common CRASH_ADDR_LOW_MAX
definition for both x86 32-bit and 64-bit(32-bit x86 has the same value defined for
CRASH_ADDR_LOW_MAX and CRASH_ADDR_HIGH_MAX), so old kexec will load below
CRASH_ADDR_LOW_MAX, so I think the description is fine :-)

Regards,
Xunlei

Post by Dave Young
So it looks better to just drop the one line comment without adding
further comments here.

Post by Xunlei Pang
*/
crash_base = memblock_find_in_range(CRASH_ALIGN,
high ? CRASH_ADDR_HIGH_MAX
--
1.8.3.1

Thanks
Dave
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