Re: [PATCH v2 4/7] s390/physmem_info: query diag500(STORAGE LIMIT) to support QEMU/KVM memory devices

[Alexander Gordeev]

On Mon, Oct 14, 2024 at 04:46:16PM +0200, David Hildenbrand wrote:

Hi David!

> @@ -157,7 +189,9 @@ unsigned long detect_max_physmem_end(void)
>  {
>  	unsigned long max_physmem_end = 0;
>  
> -	if (!sclp_early_get_memsize(&max_physmem_end)) {
> +	if (!diag500_storage_limit(&max_physmem_end)) {
> +		physmem_info.info_source = MEM_DETECT_DIAG500_STOR_LIMIT;
> +	} else if (!sclp_early_get_memsize(&max_physmem_end)) {
>  		physmem_info.info_source = MEM_DETECT_SCLP_READ_INFO;
>  	} else {
>  		max_physmem_end = search_mem_end();
> @@ -170,11 +204,17 @@ void detect_physmem_online_ranges(unsigned long max_physmem_end)
>  {
>  	if (!sclp_early_read_storage_info()) {
>  		physmem_info.info_source = MEM_DETECT_SCLP_STOR_INFO;
> +		return;
>  	} else if (!diag260()) {
>  		physmem_info.info_source = MEM_DETECT_DIAG260;
> -	} else if (max_physmem_end) {
> -		add_physmem_online_range(0, max_physmem_end);
> +		return;
> +	} else if (physmem_info.info_source == MEM_DETECT_DIAG500_STOR_LIMIT) {
> +		max_physmem_end = 0;
> +		if (!sclp_early_get_memsize(&max_physmem_end))
> +			physmem_info.info_source = MEM_DETECT_SCLP_READ_INFO;

Why search_mem_end() is not tried in case sclp_early_get_memsize() failed?

>  	}
> +	if (max_physmem_end)
> +		add_physmem_online_range(0, max_physmem_end);
>  }
>  
>  void physmem_set_usable_limit(unsigned long limit)
> diff --git a/arch/s390/include/asm/physmem_info.h b/arch/s390/include/asm/physmem_info.h
> index f45cfc8bc233..51b68a43e195 100644
> --- a/arch/s390/include/asm/physmem_info.h
> +++ b/arch/s390/include/asm/physmem_info.h
> @@ -9,6 +9,7 @@ enum physmem_info_source {
>  	MEM_DETECT_NONE = 0,
>  	MEM_DETECT_SCLP_STOR_INFO,
>  	MEM_DETECT_DIAG260,
> +	MEM_DETECT_DIAG500_STOR_LIMIT,
>  	MEM_DETECT_SCLP_READ_INFO,
>  	MEM_DETECT_BIN_SEARCH
>  };
> @@ -107,6 +108,8 @@ static inline const char *get_physmem_info_source(void)
>  		return "sclp storage info";
>  	case MEM_DETECT_DIAG260:
>  		return "diag260";
> +	case MEM_DETECT_DIAG500_STOR_LIMIT:
> +		return "diag500 storage limit";

AFAIU you want to always override MEM_DETECT_DIAG500_STOR_LIMIT method
with an online memory detection method. In that case this code is dead.

>  	case MEM_DETECT_SCLP_READ_INFO:
>  		return "sclp read info";
>  	case MEM_DETECT_BIN_SEARCH:

Thanks!