Re: [PATCH v4] s390/iomem: register initrd as an iomem resource when retain_initrd is set

[Ilya Leoshkevich <iii@linux.ibm.com>]

On 8/18/26 19:57, Joseph Cathcart wrote:
> Currently, /proc/iomem contains no reference to initrd memory, even
> when initrd is retained and still held in RAM. This makes the memory
> ranges invisible from userspace, and unusable to programs such as
> kexec. (A sysfs bin file is created for initrd, but this doesn't
> help programs which need the explicit memory ranges)
> 
> Add initrd to standard_resources[] unconditionally. Add initrd as a
> child of iomem_resources only if retain_initrd is specified.
> 
> strstr() could match substrings like "retain_initrd=0" or
> "no_retain_initrd", but this is how PPC chose to check for
> "retain_initrd" param too. (arch/powerpc/kexec/ranges.c)
> 
> Signed-off-by: Joseph Cathcart <josephc@linux.ibm.com>
> ---
>   arch/s390/kernel/setup.c | 22 ++++++++++++++++++++++
>   1 file changed, 22 insertions(+)

Checkpatch complains:

$ b4 shazam 
'https://lore.kernel.org/all/20260818175755.3520-1-josephc@linux.ibm.com/'

$ git format-patch -1 --stdout | ./scripts/checkpatch.pl -
ERROR: trailing whitespace
#58: FILE: arch/s390/kernel/setup.c:513:
+^I$

> diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
> index b60284328fe3..373e54ed7519 100644
> --- a/arch/s390/kernel/setup.c
> +++ b/arch/s390/kernel/setup.c
> @@ -481,15 +481,22 @@ static struct resource bss_resource = {
>   	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
>   };
>   
> +static struct resource initrd_resource = {
> +	.name = "initrd",
> +	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
> +};
> +
>   static struct resource __initdata *standard_resources[] = {
>   	&code_resource,
>   	&data_resource,
>   	&bss_resource,
> +	&initrd_resource,
>   };
>   
>   static void __init setup_resources(void)
>   {
>   	struct resource *res, *std_res, *sub_res;
> +	bool retain_initrd = false;
>   	phys_addr_t start, end;
>   	int j;
>   	u64 i;
> @@ -501,6 +508,19 @@ static void __init setup_resources(void)
>   	bss_resource.start = __pa_symbol(__bss_start);
>   	bss_resource.end = __pa_symbol(__bss_stop) - 1;
>   
> +	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD)) {
> +		unsigned long initrd_addr, initrd_size;
> +	
> +		if (strstr(boot_command_line, "retain_initrd"))
> +			retain_initrd = true;
> +		if (retain_initrd && get_physmem_reserved(RR_INITRD, &initrd_addr, &initrd_size)) {
> +			initrd_resource.start = initrd_addr;
> +			initrd_resource.end = initrd_resource.start + initrd_size - 1;
> +		} else {
> +			retain_initrd = false;
> +		}
> +	}
> +
>   	for_each_mem_range(i, &start, &end) {
>   		res = memblock_alloc_or_panic(sizeof(*res), 8);
>   		res->flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM;
> @@ -517,6 +537,8 @@ static void __init setup_resources(void)
>   
>   		for (j = 0; j < ARRAY_SIZE(standard_resources); j++) {
>   			std_res = standard_resources[j];
> +			if (std_res == &initrd_resource && !retain_initrd)
> +				continue;
>   			if (std_res->start < res->start ||
>   			    std_res->start > res->end)
>   				continue;

Cc: Christian and Alexander.

I wonder if it would make sense to move initrd resource creation to
do_populate_rootfs(), right after /sys/firmware/initrd creation,
enabling this feature on all architectures?