[PATCH v19 11/13] arm64: kdump: reimplement crashkernel=X

Zhen Lei
2021-12-28T13:29:59Z

From: Chen Zhou <chenzhou10@huawei.com>

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@huawei.com>
Co-developed-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
arch/arm64/kernel/machine_kexec.c | 5 +++-
arch/arm64/kernel/machine_kexec_file.c | 12 ++++++--
arch/arm64/kernel/setup.c | 13 +++++++-
arch/arm64/mm/init.c | 41 ++++++++++----------------
4 files changed, 42 insertions(+), 29 deletions(-)

diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index 6fb31c117ebe08c..6665bf31f6b6a19 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -327,7 +327,10 @@ bool crash_is_nosave(unsigned long pfn)

/* in reserved memory? */
addr = __pfn_to_phys(pfn);
- if ((addr < crashk_res.start) || (crashk_res.end < addr))
+ if (((addr < crashk_res.start) || (crashk_res.end < addr)) && !crashk_low_res.end)
+ return false;
+
+ if ((addr < crashk_low_res.start) || (crashk_low_res.end < addr))
return false;

if (!kexec_crash_image)
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 59c648d51848886..889951291cc0f9c 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..91b8038a1529068 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -74,41 +74,32 @@ phys_addr_t arm64_dma_phys_limit __ro_after_init;
*/
static void __init reserve_crashkernel(void)
{
- unsigned long long crash_base, crash_size;
- unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
+ unsigned long long crash_size, crash_base, total_mem, low_size;
+ bool high = false;
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;
+ total_mem = memblock_phys_mem_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;
+ ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
+ if (ret != 0 || crash_size <= 0) {
+ /* crashkernel=X,high and possible crashkernel=Y,low */
+ ret = parse_crashkernel_high_low(boot_command_line, &crash_size, &low_size);
+ if (ret)
+ return;
+ high = true;
}

- pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
- crash_base, crash_base + crash_size, crash_size >> 20);
+ ret = reserve_crashkernel_mem(total_mem, crash_size, crash_base, low_size, high);
+ if (ret)
+ return;

/*
* 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;
+ kmemleak_ignore_phys(crashk_res.start);
+ if (crashk_low_res.end)
+ kmemleak_ignore_phys(crashk_low_res.start);
}
#else
static void __init reserve_crashkernel(void)
--
2.25.1