[PATCH v16 07/11] arm64: kdump: reimplement crashkernel=X

From: Zhen Lei
Date: Tue Nov 23 2021 - 07:50:07 EST

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From: Chen Zhou <chenzhou10@xxxxxxxxxx>

There are following issues in arm64 kdump:
1. We use crashkernel=X to reserve crashkernel below 4G, which
will fail when there is no enough low memory.
2. If reserving crashkernel above 4G, in this case, crash dump
kernel will boot failure because there is no low memory available
for allocation.

To solve these issues, change the behavior of crashkernel=X and
introduce crashkernel=X,[high,low]. crashkernel=X tries low allocation
in DMA zone, and fall back to high allocation if it fails.
We can also use "crashkernel=X,high" to select a region above DMA zone,
which also tries to allocate at least 256M in DMA zone automatically.
"crashkernel=Y,low" can be used to allocate specified size low memory.

Another minor change, there may be two regions reserved for crash
dump kernel, in order to distinct from the high region and make no
effect to the use of existing kexec-tools, rename the low region as
"Crash kernel (low)".

Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx>
Tested-by: John Donnelly <John.p.donnelly@xxxxxxxxxx>
---
arch/arm64/include/asm/kexec.h | 4 ++
arch/arm64/kernel/machine_kexec_file.c | 12 +++++-
arch/arm64/kernel/setup.c | 13 +++++-
arch/arm64/mm/init.c | 59 +++++---------------------
kernel/crash_core.c | 6 +--
5 files changed, 40 insertions(+), 54 deletions(-)

diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 1b9edc69f0244ca..3bde0079925d771 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -96,6 +96,10 @@ static inline void crash_prepare_suspend(void) {}
static inline void crash_post_resume(void) {}
#endif

+#ifdef CONFIG_KEXEC_CORE
+extern void __init reserve_crashkernel(void);
+#endif
+
#if defined(CONFIG_KEXEC_CORE)
void cpu_soft_restart(unsigned long el2_switch, unsigned long entry,
unsigned long arg0, unsigned long arg1,
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 63634b4d72c158f..6f3fa059ca4e816 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -65,10 +65,18 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)

/* Exclude crashkernel region */
ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
+ if (ret)
+ goto out;
+
+ if (crashk_low_res.end) {
+ ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
+ if (ret)
+ goto out;
+ }

- if (!ret)
- ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
+ ret = crash_prepare_elf64_headers(cmem, true, addr, sz);

+out:
kfree(cmem);
return ret;
}
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index be5f85b0a24de69..4bb2e55366be64d 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -248,7 +248,18 @@ static void __init request_standard_resources(void)
kernel_data.end <= res->end)
request_resource(res, &kernel_data);
#ifdef CONFIG_KEXEC_CORE
- /* Userspace will find "Crash kernel" region in /proc/iomem. */
+ /*
+ * Userspace will find "Crash kernel" or "Crash kernel (low)"
+ * region in /proc/iomem.
+ * In order to distinct from the high region and make no effect
+ * to the use of existing kexec-tools, rename the low region as
+ * "Crash kernel (low)".
+ */
+ if (crashk_low_res.end && crashk_low_res.start >= res->start &&
+ crashk_low_res.end <= res->end) {
+ crashk_low_res.name = "Crash kernel (low)";
+ request_resource(res, &crashk_low_res);
+ }
if (crashk_res.end && crashk_res.start >= res->start &&
crashk_res.end <= res->end)
request_resource(res, &crashk_res);
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index be4595dc7459115..85c83e4eff2b6c4 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -36,6 +36,7 @@
#include <asm/fixmap.h>
#include <asm/kasan.h>
#include <asm/kernel-pgtable.h>
+#include <asm/kexec.h>
#include <asm/kvm_host.h>
#include <asm/memory.h>
#include <asm/numa.h>
@@ -64,57 +65,11 @@ EXPORT_SYMBOL(memstart_addr);
*/
phys_addr_t arm64_dma_phys_limit __ro_after_init;

-#ifdef CONFIG_KEXEC_CORE
-/*
- * reserve_crashkernel() - reserves memory for crash kernel
- *
- * This function reserves memory area given in "crashkernel=" kernel command
- * line parameter. The memory reserved is used by dump capture kernel when
- * primary kernel is crashing.
- */
+#ifndef CONFIG_KEXEC_CORE
static void __init reserve_crashkernel(void)
{
- unsigned long long crash_base, crash_size;
- unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
- int ret;
-
- ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
- &crash_size, &crash_base);
- /* no crashkernel= or invalid value specified */
- if (ret || !crash_size)
- return;
-
- crash_size = PAGE_ALIGN(crash_size);
-
- /* User specifies base address explicitly. */
- if (crash_base)
- crash_max = crash_base + crash_size;
-
- /* Current arm64 boot protocol requires 2MB alignment */
- crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
- crash_base, crash_max);
- if (!crash_base) {
- pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
- crash_size);
- return;
- }
-
- pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
- crash_base, crash_base + crash_size, crash_size >> 20);
-
- /*
- * The crashkernel memory will be removed from the kernel linear
- * map. Inform kmemleak so that it won't try to access it.
- */
- kmemleak_ignore_phys(crash_base);
- crashk_res.start = crash_base;
- crashk_res.end = crash_base + crash_size - 1;
}
-#else
-static void __init reserve_crashkernel(void)
-{
-}
-#endif /* CONFIG_KEXEC_CORE */
+#endif

/*
* Return the maximum physical address for a zone accessible by the given bits
@@ -362,6 +317,14 @@ void __init bootmem_init(void)
* reserved, so do it here.
*/
reserve_crashkernel();
+#ifdef CONFIG_KEXEC_CORE
+ /*
+ * The low region is intended to be used for crash dump kernel devices,
+ * just mark the low region as "nomap" simply.
+ */
+ if (crashk_low_res.end)
+ memblock_mark_nomap(crashk_low_res.start, resource_size(&crashk_low_res));
+#endif

memblock_dump_all();
}
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 336794a5abc6997..4dc2643fcbccf99 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -323,10 +323,10 @@ int __init parse_crashkernel_low(char *cmdline,

#ifdef CONFIG_KEXEC_CORE

-#ifdef CONFIG_X86
+#if defined(CONFIG_X86) || defined(CONFIG_ARM64)
static int __init reserve_crashkernel_low(void)
{
-#ifdef CONFIG_X86_64
+#ifdef CONFIG_64BIT
unsigned long long base, low_base = 0, low_size = 0;
unsigned long low_mem_limit;
int ret;
@@ -451,7 +451,7 @@ void __init reserve_crashkernel(void)
crashk_res.start = crash_base;
crashk_res.end = crash_base + crash_size - 1;
}
-#endif /* CONFIG_X86 */
+#endif
#endif /* CONFIG_KEXEC_CORE */

Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
--
2.25.1

Next message: Sean Nyekjaer: "Re: [PATCH v5 3/4] mtd: core: protect access to MTD devices while in suspend"
Previous message: Zhen Lei: "[PATCH v16 09/11] of: fdt: Aggregate the processing of "linux,usable-memory-range""
In reply to: Zhen Lei: "[PATCH v16 09/11] of: fdt: Aggregate the processing of "linux,usable-memory-range""
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