Re: [PATCH v1] kexec-tools/s390: add --reuseinitrd support

[Joseph Cathcart <josephc@linux.ibm.com>]

On 8/18/26 4:39 PM, Joseph Cathcart wrote:
> Currently, the --reuseinitrd param is not supported on s390. This
> prevents testing kexec in environments such as virtme-ng, which by
> default does not store the initrd on disk.
>
> When --reuseinitrd is specified, add retained initrd memory range to
> memory_range[] and fill new kernel parmarea directly with retained
> initrd base and size, rather than memory range of a new ramdisk.
>
> Add die() cases for trying to use --reuseinitrd flag in addition to
> --ramdisk or --initrd, and for using --kexec-file-syscall instead of
> --kexec-syscall while trying to use --reuseinitrd.
>
> Signed-off-by: Joseph Cathcart <josephc@linux.ibm.com>
> ---
>
> Depends on: https://lore.kernel.org/linux-s390/20260818153559.5700-1-josephc@linux.ibm.com/T/#u
>
>   kexec/arch/s390/Makefile      |  2 ++
>   kexec/arch/s390/kexec-image.c | 11 ++++++++++-
>   kexec/arch/s390/kexec-s390.c  | 17 +++++++++++++++--
>   kexec/arch/s390/kexec-s390.h  |  2 ++
>   4 files changed, 29 insertions(+), 3 deletions(-)
>
> diff --git a/kexec/arch/s390/Makefile b/kexec/arch/s390/Makefile
> index fab3e68..17f9dc8 100644
> --- a/kexec/arch/s390/Makefile
> +++ b/kexec/arch/s390/Makefile
> @@ -6,6 +6,8 @@ s390_KEXEC_SRCS += kexec/arch/s390/kexec-image.c
>   s390_KEXEC_SRCS += kexec/arch/s390/kexec-elf-rel-s390.c
>   s390_KEXEC_SRCS += kexec/arch/s390/crashdump-s390.c
>   
> +s390_ARCH_REUSE_INITRD =
> +
>   dist += kexec/arch/s390/Makefile $(s390_KEXEC_SRCS)			\
>   	kexec/arch/s390/kexec-s390.h					\
>   	kexec/arch/s390/include/arch/options.h
> diff --git a/kexec/arch/s390/kexec-image.c b/kexec/arch/s390/kexec-image.c
> index 69aaf96..1a59a32 100644
> --- a/kexec/arch/s390/kexec-image.c
> +++ b/kexec/arch/s390/kexec-image.c
> @@ -78,6 +78,9 @@ int image_s390_load_file(int argc, char **argv, struct kexec_info *info)
>   		}
>   	}
>   
> +	if (reuse_initrd)
> +		die("--reuseinitrd not supported with --kexec-file-syscall. Please use --kexec-syscall\n");
> +
>   	if (ramdisk) {
>   		info->initrd_fd = open(ramdisk, O_RDONLY);
>   		if (info->initrd_fd == -1) {
> @@ -104,7 +107,7 @@ image_s390_load(int argc, char **argv, const char *kernel_buf,
>   	char *rd_buffer;
>   	const char *ramdisk;
>   	off_t ramdisk_len;
> -	unsigned int ramdisk_origin;
> +	unsigned long long ramdisk_origin;
>   	int opt, ret = -1;
>   
>   	if (info->file_mode)
> @@ -137,6 +140,9 @@ image_s390_load(int argc, char **argv, const char *kernel_buf,
>   		}
>   	}
>   
> +	if (ramdisk && reuse_initrd)
> +		die("Can't specify --ramdisk or --initrd with --reuseinitrd\n");
> +
>   	if (info->kexec_flags & KEXEC_ON_CRASH) {
>   		if (parse_iomem_single("Crash kernel\n", &crash_base,
>   				       &crash_end))
> @@ -165,6 +171,9 @@ image_s390_load(int argc, char **argv, const char *kernel_buf,
>   		ramdisk_origin = _ALIGN_UP(ramdisk_origin, 0x100000);
>   		add_segment_check(info, rd_buffer, ramdisk_len,
>   				  ramdisk_origin, ramdisk_len);
> +	} else if (reuse_initrd) {
> +		ramdisk_origin = retained_initrd_base;
> +		ramdisk_len = retained_initrd_size;
>   	}
>   	if (info->kexec_flags & KEXEC_ON_CRASH) {
>   		if (load_crashdump_segments(info, crash_base, crash_end))
> diff --git a/kexec/arch/s390/kexec-s390.c b/kexec/arch/s390/kexec-s390.c
> index 86c9fb8..4e77fc4 100644
> --- a/kexec/arch/s390/kexec-s390.c
> +++ b/kexec/arch/s390/kexec-s390.c
> @@ -25,6 +25,13 @@
>   #include <arch/options.h>
>   
>   static struct memory_range memory_range[MAX_MEMORY_RANGES];
> +unsigned long long retained_initrd_base, retained_initrd_size;
> +unsigned int reuse_initrd = 0;
> +
> +void arch_reuse_initrd(void)
> +{
> +	reuse_initrd = 1;
> +}
>   
>   /*
>    * Read string from file
> @@ -151,6 +158,7 @@ int get_memory_ranges_s390(struct memory_range memory_range[], int *ranges,
>   {
>   	char crash_kernel[] = "Crash kernel\n";
>   	char sys_ram[] = "System RAM\n";
> +	char kernel_initrd[] = "initrd\n";
>   	const char *iomem = proc_iomem();
>   	FILE *fp;
>   	char line[80];
> @@ -174,11 +182,16 @@ int get_memory_ranges_s390(struct memory_range memory_range[], int *ranges,
>   		sscanf(line,"%llx-%llx : %n", &start, &end, &cons);
>   		str = line+cons;
>   		if ((memcmp(str, sys_ram, strlen(sys_ram)) == 0) ||
> -		    ((memcmp(str, crash_kernel, strlen(crash_kernel)) == 0) &&
> -		     with_crashk)) {
> +			((memcmp(str, kernel_initrd, strlen(kernel_initrd)) == 0) && reuse_initrd) ||
> +			((memcmp(str, crash_kernel, strlen(crash_kernel)) == 0) && with_crashk)) {
>   			memory_range[current_range].start = start;
>   			memory_range[current_range].end = end;
>   			memory_range[current_range].type = RANGE_RAM;
> +			if (memcmp(str, kernel_initrd, strlen(kernel_initrd)) == 0) {
> +				retained_initrd_base = start;
> +				retained_initrd_size = end - start + 1;
> +			}
> +
>   			current_range++;
>   		}
>   		else {
> diff --git a/kexec/arch/s390/kexec-s390.h b/kexec/arch/s390/kexec-s390.h
> index 6a99518..a990739 100644
> --- a/kexec/arch/s390/kexec-s390.h
> +++ b/kexec/arch/s390/kexec-s390.h
> @@ -34,5 +34,7 @@ extern int load_crashdump_segments(struct kexec_info *info,
>   extern int get_memory_ranges_s390(struct memory_range range[], int *ranges,
>   				  int with_crashk);
>   extern int command_line_add(struct kexec_info *info, const char *str);
> +extern unsigned long long retained_initrd_base, retained_initrd_size;
> +extern unsigned int reuse_initrd;
>   
>   #endif /* KEXEC_S390_H */