[PATCH v3 2/2] arm64: kdump: Support crashkernel=X fall back to reserve region above DMA zones

Zhen Lei
2022-07-11T09:04:57Z

For crashkernel=X without '@offset', select a region within DMA zones
first, and fall back to reserve region above DMA zones. This allows
users to use the same configuration on multiple platforms.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
Documentation/admin-guide/kernel-parameters.txt | 2 +-
arch/arm64/mm/init.c | 16 +++++++++++++++-
2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 65a2c3a22a4b57d..cb6a346419a1fe0 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -823,7 +823,7 @@
memory region [offset, offset + size] for that kernel
image. If '@offset' is omitted, then a suitable offset
is selected automatically.
- [KNL, X86-64] Select a region under 4G first, and
+ [KNL, X86-64, ARM64] Select a region under 4G first, and
fall back to reserve region above 4G when '@offset'
hasn't been specified.
See Documentation/admin-guide/kdump/kdump.rst for further details.
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 5390f361208ccf7..8539598f9e58b4d 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -138,6 +138,7 @@ static void __init reserve_crashkernel(void)
unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
char *cmdline = boot_command_line;
int ret;
+ bool fixed_base;

if (!IS_ENABLED(CONFIG_KEXEC_CORE))
return;
@@ -166,15 +167,28 @@ static void __init reserve_crashkernel(void)
return;
}

+ fixed_base = !!crash_base;
crash_size = PAGE_ALIGN(crash_size);

/* User specifies base address explicitly. */
- if (crash_base)
+ if (fixed_base)
crash_max = crash_base + crash_size;

+retry:
crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
crash_base, crash_max);
if (!crash_base) {
+ /*
+ * Attempt to fully allocate low memory failed, fall back
+ * to high memory, the minimum required low memory will be
+ * reserved later.
+ */
+ if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) {
+ crash_max = CRASH_ADDR_HIGH_MAX;
+ crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
+ goto retry;
+ }
+
pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
crash_size);
return;
--
2.25.1