Re: [V3 PATCH 09/16] powerpc/pseries/vas: Implement to get all capabilities

[Nicholas Piggin <npiggin@gmail.com>]

Excerpts from Haren Myneni's message of April 18, 2021 7:08 am:
> 
> pHyp provides various VAS capabilities such as GZIP default and QoS
> capabilities which are used to determine total number of credits
> available in LPAR, maximum window credits, maximum LPAR credits,
> whether usermode copy/paste is supported, and etc.
> 
> So first retrieve overall vas capabilities using
> H_QUERY_VAS_CAPABILITIES HCALL which tells the specific features that
> are available. Then retrieve the specific capabilities by using the
> feature type in H_QUERY_VAS_CAPABILITIES HCALL.
> 
> pHyp supports only GZIP default and GZIP QoS capabilities right now.

Changelog and title could use a bit of work.

> 
> Signed-off-by: Haren Myneni <haren@linux.ibm.com>
> ---
>  arch/powerpc/platforms/pseries/vas.c | 130 +++++++++++++++++++++++++++
>  1 file changed, 130 insertions(+)
> 
> diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c
> index 06960151477c..35946fb02995 100644
> --- a/arch/powerpc/platforms/pseries/vas.c
> +++ b/arch/powerpc/platforms/pseries/vas.c
> @@ -30,6 +30,13 @@
>  /* phyp allows one credit per window right now */
>  #define DEF_WIN_CREDS		1
>  
> +static struct vas_all_capabs capabs_all;

Does this name come from PAPR? If not, capabilities or caps are better 
for readability than capabs.

> +static int copypaste_feat;

Should be a bool? And what does it mean? copy-paste is a host core 
capability.

> +
> +struct vas_capabs vcapabs[VAS_MAX_FEAT_TYPE];
> +
> +DEFINE_MUTEX(vas_pseries_mutex);

Can these be made static if they're only used here, and export them if a 
future patch uses them (or add the header declaration now).


> +
>  static int64_t hcall_return_busy_check(int64_t rc)
>  {
>  	/* Check if we are stalled for some time */
> @@ -215,3 +222,126 @@ int plpar_vas_query_capabilities(const u64 hcall, u8 query_type,
>  		return -EIO;
>  	}
>  }
> +
> +/*
> + * Get the specific capabilities based on the feature type.
> + * Right now supports GZIP default and GZIP QoS capabilities.
> + */
> +static int get_vas_capabilities(u8 feat, enum vas_cop_feat_type type,
> +				struct vas_ct_capabs_be *capab_be)
> +{
> +	struct vas_ct_capabs *capab;
> +	struct vas_capabs *vcapab;
> +	int rc = 0;
> +
> +	vcapab = &vcapabs[type];
> +	memset(vcapab, 0, sizeof(*vcapab));
> +	INIT_LIST_HEAD(&vcapab->list);
> +
> +	capab = &vcapab->capab;
> +
> +	rc = plpar_vas_query_capabilities(H_QUERY_VAS_CAPABILITIES, feat,
> +					  (u64)virt_to_phys(capab_be));
> +	if (rc)
> +		return rc;
> +
> +	capab->user_mode = capab_be->user_mode;
> +	if (!(capab->user_mode & VAS_COPY_PASTE_USER_MODE)) {
> +		pr_err("User space COPY/PASTE is not supported\n");
> +		return -ENOTSUPP;
> +	}
> +
> +	snprintf(capab->name, VAS_DESCR_LEN + 1, "%.8s",
> +		 (char *)&capab_be->descriptor);
> +	capab->descriptor = be64_to_cpu(capab_be->descriptor);
> +	capab->win_type = capab_be->win_type;
> +	if (capab->win_type >= VAS_MAX_FEAT_TYPE) {
> +		pr_err("Unsupported window type %u\n", capab->win_type);
> +		return -EINVAL;
> +	}
> +	capab->max_lpar_creds = be16_to_cpu(capab_be->max_lpar_creds);
> +	capab->max_win_creds = be16_to_cpu(capab_be->max_win_creds);
> +	atomic_set(&capab->target_lpar_creds,
> +		   be16_to_cpu(capab_be->target_lpar_creds));
> +	if (feat == VAS_GZIP_DEF_FEAT) {
> +		capab->def_lpar_creds = be16_to_cpu(capab_be->def_lpar_creds);
> +
> +		if (capab->max_win_creds < DEF_WIN_CREDS) {
> +			pr_err("Window creds(%u) > max allowed window creds(%u)\n",
> +			       DEF_WIN_CREDS, capab->max_win_creds);
> +			return -EINVAL;
> +		}
> +	}
> +
> +	copypaste_feat = 1;
> +
> +	return 0;
> +}
> +
> +static int __init pseries_vas_init(void)
> +{
> +	struct vas_ct_capabs_be *ct_capabs_be;
> +	struct vas_all_capabs_be *capabs_be;
> +	int rc;
> +
> +	/*
> +	 * Linux supports user space COPY/PASTE only with Radix
> +	 */
> +	if (!radix_enabled()) {
> +		pr_err("API is supported only with radix page tables\n");
> +		return -ENOTSUPP;
> +	}
> +
> +	capabs_be = kmalloc(sizeof(*capabs_be), GFP_KERNEL);
> +	if (!capabs_be)
> +		return -ENOMEM;
> +	/*
> +	 * Get VAS overall capabilities by passing 0 to feature type.
> +	 */
> +	rc = plpar_vas_query_capabilities(H_QUERY_VAS_CAPABILITIES, 0,
> +					  (u64)virt_to_phys(capabs_be));
> +	if (rc)
> +		goto out;
> +
> +	snprintf(capabs_all.name, VAS_DESCR_LEN, "%.7s",
> +		 (char *)&capabs_be->descriptor);
> +	capabs_all.descriptor = be64_to_cpu(capabs_be->descriptor);
> +	capabs_all.feat_type = be64_to_cpu(capabs_be->feat_type);
> +
> +	ct_capabs_be = kmalloc(sizeof(*ct_capabs_be), GFP_KERNEL);
> +	if (!ct_capabs_be) {
> +		rc = -ENOMEM;
> +		goto out;
> +	}
> +	/*
> +	 * QOS capabilities available
> +	 */
> +	if (capabs_all.feat_type & VAS_GZIP_QOS_FEAT_BIT) {
> +		rc = get_vas_capabilities(VAS_GZIP_QOS_FEAT,
> +					  VAS_GZIP_QOS_FEAT_TYPE, ct_capabs_be);
> +
> +		if (rc)
> +			goto out_ct;
> +	}
> +	/*
> +	 * Default capabilities available
> +	 */
> +	if (capabs_all.feat_type & VAS_GZIP_DEF_FEAT_BIT) {
> +		rc = get_vas_capabilities(VAS_GZIP_DEF_FEAT,
> +					  VAS_GZIP_DEF_FEAT_TYPE, ct_capabs_be);
> +		if (rc)
> +			goto out_ct;
> +	}

Using the same buffer for two hcalls? Do they fill in different parts of 
it?

> +
> +	if (!copypaste_feat)
> +		pr_err("GZIP feature is not supported\n");

This is dead code AFAIKS, because errors will always branch to out.

Thanks,
Nick

> +
> +	pr_info("GZIP feature is available\n");
> +
> +out_ct:
> +	kfree(ct_capabs_be);
> +out:
> +	kfree(capabs_be);
> +	return rc;
> +}
> +machine_device_initcall(pseries, pseries_vas_init);
> -- 
> 2.18.2
> 
> 
>