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Message-ID: <55a6470c-1ce5-b237-d3be-1b98e4dbe3ce@redhat.com>
Date:   Wed, 29 Jun 2022 12:00:50 +0200
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From:   Hans de Goede <hdegoede@redhat.com>
Subject: Re: [PATCH] platform/x86: ISST: PUNIT device mapping with Sub-NUMA
 clustering
To:     Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        markgross@kernel.org
Cc:     platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20220627215031.2158825-1-srinivas.pandruvada@linux.intel.com>
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In-Reply-To: <20220627215031.2158825-1-srinivas.pandruvada@linux.intel.com>
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Hi,

On 6/27/22 23:50, Srinivas Pandruvada wrote:
> On a multiple package system using Sub-NUMA clustering, there is an issue
> in mapping Linux CPU number to PUNIT PCI device when manufacturer decided
> to reuse the PCI bus number across packages. Bus number can be reused as
> long as they are in different domain or segment. In this case some CPU
> will fail to find a PCI device to issue SST requests.
> 
> When bus numbers are reused across CPU packages, we are using proximity
> information by matching CPU numa node id to PUNIT PCI device numa node
> id. But on a package there can be only one PUNIT PCI device, but multiple
> numa nodes (one for each sub cluster). So, the numa node ID of the PUNIT
> PCI device can only match with one numa node id of CPUs in a sub cluster
> in the package.
> 
> Since there can be only one PUNIT PCI device per package, if we match
> with numa node id of any sub cluster in that package, we can use that
> mapping for any CPU in that package. So, store the match information
> in a per package data structure and return the information when there
> is no match.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> ---
>  .../intel/speed_select_if/isst_if_common.c    | 22 +++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/drivers/platform/x86/intel/speed_select_if/isst_if_common.c b/drivers/platform/x86/intel/speed_select_if/isst_if_common.c
> index e8424e70d81d..f3cd1be3283a 100644
> --- a/drivers/platform/x86/intel/speed_select_if/isst_if_common.c
> +++ b/drivers/platform/x86/intel/speed_select_if/isst_if_common.c
> @@ -286,11 +286,18 @@ struct isst_if_cpu_info {
>  	int numa_node;
>  };
>  
> +struct isst_if_pkg_info {
> +	struct pci_dev *pci_dev[2];

This and (continued below) ...

> +};
> +
>  static struct isst_if_cpu_info *isst_cpu_info;
> +static struct isst_if_pkg_info *isst_pkg_info;
> +
>  #define ISST_MAX_PCI_DOMAINS	8
>  
>  static struct pci_dev *_isst_if_get_pci_dev(int cpu, int bus_no, int dev, int fn)
>  {
> +	int pkg_id = topology_physical_package_id(cpu);
>  	struct pci_dev *matched_pci_dev = NULL;
>  	struct pci_dev *pci_dev = NULL;
>  	int no_matches = 0;
> @@ -324,6 +331,8 @@ static struct pci_dev *_isst_if_get_pci_dev(int cpu, int bus_no, int dev, int fn
>  		}
>  
>  		if (node == isst_cpu_info[cpu].numa_node) {
> +			isst_pkg_info[pkg_id].pci_dev[bus_no] = _pci_dev;
> +

This and ...

>  			pci_dev = _pci_dev;
>  			break;
>  		}
> @@ -342,6 +351,9 @@ static struct pci_dev *_isst_if_get_pci_dev(int cpu, int bus_no, int dev, int fn
>  	if (!pci_dev && no_matches == 1)
>  		pci_dev = matched_pci_dev;
>  
> +	if (!pci_dev)
> +		pci_dev = isst_pkg_info[pkg_id].pci_dev[bus_no];
> +

This assumes that bus_no is never > 1, is this assumption enforced somewhere?

Also maybe make the 2 in:

> +struct isst_if_pkg_info {
> +	struct pci_dev *pci_dev[2];

a #define ?

Regards,

Hans


>  	return pci_dev;
>  }
>  
> @@ -417,10 +429,19 @@ static int isst_if_cpu_info_init(void)
>  	if (!isst_cpu_info)
>  		return -ENOMEM;
>  
> +	isst_pkg_info = kcalloc(topology_max_packages(),
> +				sizeof(*isst_pkg_info),
> +				GFP_KERNEL);
> +	if (!isst_pkg_info) {
> +		kfree(isst_cpu_info);
> +		return -ENOMEM;
> +	}
> +
>  	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
>  				"platform/x86/isst-if:online",
>  				isst_if_cpu_online, NULL);
>  	if (ret < 0) {
> +		kfree(isst_pkg_info);
>  		kfree(isst_cpu_info);
>  		return ret;
>  	}
> @@ -433,6 +454,7 @@ static int isst_if_cpu_info_init(void)
>  static void isst_if_cpu_info_exit(void)
>  {
>  	cpuhp_remove_state(isst_if_online_id);
> +	kfree(isst_pkg_info);
>  	kfree(isst_cpu_info);
>  };
>