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Subject[PATCH 2/4] arm64: kdump: support reserving crashkernel above 4G
Date
When crashkernel is reserved above 4G in memory, kernel should
reserve some amount of low memory for swiotlb and some DMA buffers.

Meanwhile, support crashkernel=X,[high,low] in arm64. When use
crashkernel=X parameter, try low memory first and fall back to high
memory unless "crashkernel=X,high" is specified.

Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
---
arch/arm64/include/asm/kexec.h | 3 +++
arch/arm64/kernel/setup.c | 3 +++
arch/arm64/mm/init.c | 34 ++++++++++++++++++++++++++++------
3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 67e4cb7..32949bf 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -28,6 +28,9 @@

#define KEXEC_ARCH KEXEC_ARCH_AARCH64

+/* 2M alignment for crash kernel regions */
+#define CRASH_ALIGN SZ_2M
+
#ifndef __ASSEMBLY__

/**
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 413d566..82cd9a0 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -243,6 +243,9 @@ static void __init request_standard_resources(void)
request_resource(res, &kernel_data);
#ifdef CONFIG_KEXEC_CORE
/* Userspace will find "Crash kernel" region in /proc/iomem. */
+ if (crashk_low_res.end && crashk_low_res.start >= res->start &&
+ crashk_low_res.end <= res->end)
+ 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 d2adffb..3fcd739 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -74,20 +74,37 @@ phys_addr_t arm64_dma_phys_limit __ro_after_init;
static void __init reserve_crashkernel(void)
{
unsigned long long crash_base, crash_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;
+ if (ret || !crash_size) {
+ /* crashkernel=X,high */
+ ret = parse_crashkernel_high(boot_command_line,
+ memblock_phys_mem_size(),
+ &crash_size, &crash_base);
+ if (ret || !crash_size)
+ return;
+ high = true;
+ }

crash_size = PAGE_ALIGN(crash_size);

if (crash_base == 0) {
- /* Current arm64 boot protocol requires 2MB alignment */
- crash_base = memblock_find_in_range(0, ARCH_LOW_ADDRESS_LIMIT,
- crash_size, SZ_2M);
+ /*
+ * Try low memory first and fall back to high memory
+ * unless "crashkernel=size[KMG],high" is specified.
+ */
+ if (!high)
+ crash_base = memblock_find_in_range(0,
+ ARCH_LOW_ADDRESS_LIMIT,
+ crash_size, CRASH_ALIGN);
+ if (!crash_base)
+ crash_base = memblock_find_in_range(0,
+ memblock_end_of_DRAM(),
+ crash_size, CRASH_ALIGN);
if (crash_base == 0) {
pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
crash_size);
@@ -105,13 +122,18 @@ static void __init reserve_crashkernel(void)
return;
}

- if (!IS_ALIGNED(crash_base, SZ_2M)) {
+ if (!IS_ALIGNED(crash_base, CRASH_ALIGN)) {
pr_warn("cannot reserve crashkernel: base address is not 2MB aligned\n");
return;
}
}
memblock_reserve(crash_base, crash_size);

+ if (crash_base >= SZ_4G && reserve_crashkernel_low()) {
+ memblock_free(crash_base, crash_size);
+ return;
+ }
+
pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
crash_base, crash_base + crash_size, crash_size >> 20);

--
2.7.4
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