linux-kernel - Re: [PATCH 2/2] RAS: Introduce the FRU Memory Poison Manager

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Date: Wed, 14 Feb 2024 13:02:14 +0100
From: Borislav Petkov <bp@...en8.de>
To: Yazen Ghannam <yazen.ghannam@....com>
Cc: tony.luck@...el.com, linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org, avadhut.naik@....com,
	john.allen@....com, muralidhara.mk@....com,
	naveenkrishna.chatradhi@....com, sathyapriya.k@....com
Subject: Re: [PATCH 2/2] RAS: Introduce the FRU Memory Poison Manager

On Tue, Feb 13, 2024 at 09:35:16PM -0600, Yazen Ghannam wrote:
> +static unsigned int get_cpu_for_fru_num(unsigned int i)
> +{
> +	unsigned int cpu = 0;
> +
> +	/* Should there be more robust error handling if none found? */
> +	for_each_online_cpu(cpu) {

You need to block CPU hotplug operations before iterating over online
CPUs: cpus_read_lock/unlock.

> +		if (topology_physical_package_id(cpu) == i)
> +			return cpu;
> +	}
> +
> +	return cpu;
> +}

Fold this one into its single callsite.

> +
> +static void init_fmps(void)
> +{
> +	struct fru_rec *rec;
> +	unsigned int i, cpu;
> +
> +	for_each_fru(i, rec) {
> +		cpu = get_cpu_for_fru_num(i);
> +		set_fmp_fields(get_fmp(rec), cpu);
> +	}
> +}
> +
> +static int get_system_info(void)
> +{
> +	u8 model = boot_cpu_data.x86_model;

No need for that local var - just use boot_cpu_data.x86_model.

> +	/* Only load on MI300A systems for now. */
> +	if (!(model >= 0x90 && model <= 0x9f))
> +		return -ENODEV;
> +
> +	if (!cpu_feature_enabled(X86_FEATURE_AMD_PPIN)) {
> +		pr_debug("PPIN feature not available");
> +		return -ENODEV;
> +	}
> +
> +	/* Use CPU Package (Socket) as FRU for MI300 systems. */
> +	max_nr_fru = topology_max_packages();
> +	if (!max_nr_fru)
> +		return -ENODEV;
> +
> +	if (!max_nr_entries)
> +		max_nr_entries = FMPM_DEFAULT_MAX_NR_ENTRIES;
> +
> +	max_rec_len  = sizeof(struct fru_rec);
> +	max_rec_len += sizeof(struct cper_fru_poison_desc) * max_nr_entries;
> +
> +	pr_debug("max_nr_fru=%u max_nr_entries=%u, max_rec_len=%lu",
> +		 max_nr_fru, max_nr_entries, max_rec_len);
> +	return 0;
> +}
> +
> +static void deallocate_records(void)

free_records

> +{
> +	struct fru_rec *rec;
> +	int i;
> +
> +	for_each_fru(i, rec)
> +		kfree(rec);
> +
> +	kfree(fru_records);
> +}
> +
> +static int allocate_records(void)
> +{
> +	int i, ret = 0;
> +
> +	fru_records = kcalloc(max_nr_fru, sizeof(struct fru_rec *), GFP_KERNEL);
> +	if (!fru_records) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	for (i = 0; i < max_nr_fru; i++) {
> +		fru_records[i] = kzalloc(max_rec_len, GFP_KERNEL);
> +		if (!fru_records[i]) {
> +			ret = -ENOMEM;
> +			goto out_free;
> +		}
> +	}
> +
> +	return ret;
> +
> +out_free:
> +	for (; i >= 0; i--)
> +		kfree(fru_records[i]);
> +
> +	kfree(fru_records);
> +out:
> +	return ret;
> +}
> +
> +static const struct x86_cpu_id fmpm_cpuids[] = {
> +	X86_MATCH_VENDOR_FAM(AMD, 0x19, NULL),

This is why this should depend on AMD in Kconfig.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette