Re: [PATCH v11 01/11] riscv: kexec_file: Fix crashk_low_res not exclude bug

[Jinjie Ruan]

On 2026/3/30 11:49, Guo Ren wrote:
> On Sat, Mar 28, 2026 at 3:41 PM Jinjie Ruan <ruanjinjie@xxxxxxxxxx> wrote:
>>
>> As done in commit 944a45abfabc ("arm64: kdump: Reimplement crashkernel=X")
>> and commit 4831be702b95 ("arm64/kexec: Fix missing extra range for
>> crashkres_low.") for arm64, while implementing crashkernel=X,[high,low],
>> riscv should have excluded the "crashk_low_res" reserved ranges from
>> the crash kernel memory to prevent them from being exported through
>> /proc/vmcore, and the exclusion would need an extra crash_mem range.
>>
>> Cc: Guo Ren <guoren@xxxxxxxxxx>
>> Cc: Baoquan He <bhe@xxxxxxxxxx>
>> Fixes: 5882e5acf18d ("riscv: kdump: Implement crashkernel=X,[high,low]")
>> Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
>> ---
>>  arch/riscv/kernel/machine_kexec_file.c | 14 +++++++++++---
>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
>> index 54e2d9552e93..3f7766057cac 100644
>> --- a/arch/riscv/kernel/machine_kexec_file.c
>> +++ b/arch/riscv/kernel/machine_kexec_file.c
>> @@ -61,7 +61,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
>>         unsigned int nr_ranges;
>>         int ret;
>>
>> -       nr_ranges = 1; /* For exclusion of crashkernel region */
>> +       nr_ranges = 2; /* For exclusion of crashkernel region */
>>         walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
>>
>>         cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
>> @@ -76,8 +76,16 @@ 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)
>> -               ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
>> +       if (ret)
>> +               goto out;
>> +
>> +       if (crashk_low_res.end) {
>> +               ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
> Exclude crashk_low_res is reasonable, but have you tested this?

Just simply tested on qemu with crashkernel=4G with following kexec
mentioned in
https://lore.kernel.org/all/20230726175000.2536220-1-chenjiahao16@xxxxxxxxxx/.
And the second kernel can be started normally.

https://github.com/chenjh005/kexec-tools/tree/build-test-riscv-v2

# dmesg | grep crash
[    0.000000] crashkernel low memory reserved: 0xf8000000 - 0x100000000
(128 MB)
[    0.000000] crashkernel reserved: 0x000000017fe00000 -
0x000000027fe00000 (4096 MB)



> 
>> +               if (ret)
>> +                       goto out;
>> +       }
>> +
>> +       ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
>>
>>  out:
>>         kfree(cmem);
>> --
>> 2.34.1
>>
> 
>