[PATCH v22 5/9] arm64: kdump: Reimplement crashkernel=X
Zhen Lei
thunder.leizhen at huawei.com
Thu Apr 14 04:57:16 PDT 2022
From: Chen Zhou <chenzhou10 at 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 not enough low memory.
2. If reserving crashkernel above 4G, in this case, crash dump
kernel will fail to boot 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.
Signed-off-by: Chen Zhou <chenzhou10 at huawei.com>
Co-developed-by: Zhen Lei <thunder.leizhen at huawei.com>
Signed-off-by: Zhen Lei <thunder.leizhen at huawei.com>
---
arch/arm64/kernel/machine_kexec.c | 9 +-
arch/arm64/kernel/machine_kexec_file.c | 12 ++-
arch/arm64/mm/init.c | 116 +++++++++++++++++++++++--
3 files changed, 124 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index e16b248699d5c3c..19c2d487cb08feb 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -329,8 +329,13 @@ bool crash_is_nosave(unsigned long pfn)
/* in reserved memory? */
addr = __pfn_to_phys(pfn);
- if ((addr < crashk_res.start) || (crashk_res.end < addr))
- return false;
+ if ((addr < crashk_res.start) || (crashk_res.end < addr)) {
+ if (!crashk_low_res.end)
+ return false;
+
+ if ((addr < crashk_low_res.start) || (crashk_low_res.end < addr))
+ return false;
+ }
if (!kexec_crash_image)
return true;
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/mm/init.c b/arch/arm64/mm/init.c
index f670bca160992b9..99d5539c13de3b1 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -90,43 +90,138 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1;
#endif
+/* Current arm64 boot protocol requires 2MB alignment */
+#define CRASH_ALIGN SZ_2M
+
+#define CRASH_ADDR_LOW_MAX arm64_dma_phys_limit
+#define CRASH_ADDR_HIGH_MAX memblock.current_limit
+
+/*
+ * This is an empirical value in x86_64 and taken here directly. Please
+ * refer to the code comment in reserve_crashkernel_low() of x86_64 for more
+ * details.
+ */
+#define DEFAULT_CRASH_KERNEL_LOW_SIZE \
+ max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20)
+
+static int __init reserve_crashkernel_low(unsigned long long low_size)
+{
+ unsigned long long low_base;
+
+ /* passed with crashkernel=0,low ? */
+ if (!low_size)
+ return 0;
+
+ low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, 0, CRASH_ADDR_LOW_MAX);
+ if (!low_base) {
+ pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size);
+ return -ENOMEM;
+ }
+
+ pr_info("crashkernel low memory reserved: 0x%08llx - 0x%08llx (%lld MB)\n",
+ low_base, low_base + low_size, low_size >> 20);
+
+ crashk_low_res.start = low_base;
+ crashk_low_res.end = low_base + low_size - 1;
+ insert_resource(&iomem_resource, &crashk_low_res);
+
+ return 0;
+}
+
/*
* 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.
+ *
+ * NOTE: Reservation of crashkernel,low is special since its existence
+ * is not independent, need rely on the existence of crashkernel,high.
+ * Here, four cases of crashkernel low memory reservation are summarized:
+ * 1) crashkernel=Y,low is specified explicitly, the size of crashkernel low
+ * memory takes Y;
+ * 2) crashkernel=,low is not given, while crashkernel=,high is specified,
+ * take the default crashkernel low memory size;
+ * 3) crashkernel=X is specified, while fallback to get a memory region
+ * in high memory, take the default crashkernel low memory size;
+ * 4) crashkernel='invalid value',low is specified, failed the whole
+ * crashkernel reservation and bail out.
*/
static void __init reserve_crashkernel(void)
{
unsigned long long crash_base, crash_size;
- unsigned long long crash_max = arm64_dma_phys_limit;
+ unsigned long long crash_low_size;
+ unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
+ bool fixed_base, high = false;
+ char *cmdline = boot_command_line;
int ret;
if (!IS_ENABLED(CONFIG_KEXEC_CORE))
return;
- ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
+ /* crashkernel=X[@offset] */
+ ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
&crash_size, &crash_base);
- /* no crashkernel= or invalid value specified */
- if (ret || !crash_size)
- return;
+ if (ret || !crash_size) {
+ ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base);
+ if (ret || !crash_size)
+ return;
+
+ ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base);
+ if (ret == -ENOENT)
+ /* case #2 of crashkernel,low reservation */
+ crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
+ else if (ret)
+ /* case #4 of crashkernel,low reservation */
+ return;
+
+ high = true;
+ crash_max = CRASH_ADDR_HIGH_MAX;
+ }
+ 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;
- /* Current arm64 boot protocol requires 2MB alignment */
- crash_base = memblock_phys_alloc_range(crash_size, SZ_2M,
+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;
+ goto retry;
+ }
+
pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
crash_size);
return;
}
+ /*
+ * When both CONFIG_ZONE_DMA and CONFIG_ZONE_DMA32 are disabled, the
+ * CRASH_ADDR_LOW_MAX equals the upper limit of physical memory, so
+ * the 'crash_base' of high memory can not exceed it. To follow the
+ * description of "crashkernel=X,high" option, add below 'high'
+ * condition to make sure the crash low memory will be reserved.
+ */
+ if ((crash_base >= CRASH_ADDR_LOW_MAX) || high) {
+ /* case #3 of crashkernel,low reservation */
+ if (!high)
+ crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
+
+ if (reserve_crashkernel_low(crash_low_size)) {
+ memblock_phys_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);
@@ -135,6 +230,9 @@ static void __init reserve_crashkernel(void)
* map. Inform kmemleak so that it won't try to access it.
*/
kmemleak_ignore_phys(crash_base);
+ if (crashk_low_res.end)
+ kmemleak_ignore_phys(crashk_low_res.start);
+
crashk_res.start = crash_base;
crashk_res.end = crash_base + crash_size - 1;
insert_resource(&iomem_resource, &crashk_res);
--
2.25.1
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