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

Alexander Gordeev
2024-10-17T07:37:15Z

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!