[PATCH v5 5/5] x86: implement crashkernel cma reservation

Jiri Bohac
2025-06-12T10:20:05Z

Implement the crashkernel CMA reservation for x86:
- enable parsing of the cma suffix by parse_crashkernel()
- reserve memory with reserve_crashkernel_cma()
- add the CMA-reserved ranges to the e820 map for the crash kernel
- exclude the CMA-reserved ranges from vmcore

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
---
arch/x86/kernel/crash.c | 26 ++++++++++++++++++++++----
arch/x86/kernel/setup.c | 5 +++--
2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 0be61c45400c..670aa9b8b0f8 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -163,10 +163,10 @@ static struct crash_mem *fill_up_crash_elf_data(void)
return NULL;

/*
- * Exclusion of crash region and/or crashk_low_res may cause
- * another range split. So add extra two slots here.
+ * Exclusion of crash region, crashk_low_res and/or crashk_cma_ranges
+ * may cause range splits. So add extra slots here.
*/
- nr_ranges += 2;
+ nr_ranges += 2 + crashk_cma_cnt;
cmem = vzalloc(struct_size(cmem, ranges, nr_ranges));
if (!cmem)
return NULL;
@@ -184,6 +184,7 @@ static struct crash_mem *fill_up_crash_elf_data(void)
static int elf_header_exclude_ranges(struct crash_mem *cmem)
{
int ret = 0;
+ int i;

/* Exclude the low 1M because it is always reserved */
ret = crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
@@ -198,8 +199,17 @@ static int elf_header_exclude_ranges(struct crash_mem *cmem)
if (crashk_low_res.end)
ret = crash_exclude_mem_range(cmem, crashk_low_res.start,
crashk_low_res.end);
+ if (ret)
+ return ret;

- return ret;
+ for (i = 0; i < crashk_cma_cnt; ++i) {
+ ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
+ crashk_cma_ranges[i].end);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
}

static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
@@ -352,6 +362,14 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
add_e820_entry(params, &ei);
}

+ for (i = 0; i < crashk_cma_cnt; ++i) {
+ ei.addr = crashk_cma_ranges[i].start;
+ ei.size = crashk_cma_ranges[i].end -
+ crashk_cma_ranges[i].start + 1;
+ ei.type = E820_TYPE_RAM;
+ add_e820_entry(params, &ei);
+ }
+
out:
vfree(cmem);
return ret;
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 870b06571b2e..dcbeba344825 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -573,7 +573,7 @@ static void __init memblock_x86_reserve_range_setup_data(void)

static void __init arch_reserve_crashkernel(void)
{
- unsigned long long crash_base, crash_size, low_size = 0;
+ unsigned long long crash_base, crash_size, low_size = 0, cma_size = 0;
bool high = false;
int ret;

@@ -582,7 +582,7 @@ static void __init arch_reserve_crashkernel(void)

ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
&crash_size, &crash_base,
- &low_size, NULL, &high);
+ &low_size, &cma_size, &high);
if (ret)
return;

@@ -592,6 +592,7 @@ static void __init arch_reserve_crashkernel(void)
}

reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
+ reserve_crashkernel_cma(cma_size);
}

static struct resource standard_io_resources[] = {

--
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, Prague, Czechia