linux-kernel - Re: [PATCH 2/2] perf/x86/intel/uncore: With > 8 nodes, get pci bus die id from NUMA info

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Date:   Mon, 11 Jan 2021 14:00:33 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steve Wahl <steve.wahl@....com>
Cc:     rja_direct@...ups.int.hpe.com, Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        "Liang, Kan" <kan.liang@...el.com>
Subject: Re: [PATCH 2/2] perf/x86/intel/uncore: With > 8 nodes, get pci bus
 die id from NUMA info

On Fri, Jan 08, 2021 at 09:35:49AM -0600, Steve Wahl wrote:


> +		/*
> +		 * The nodeid and idmap registers only contain enough
> +		 * information to handle 8 nodes.  On systems with more
> +		 * than 8 nodes, we need to rely on NUMA information,
> +		 * filled in from BIOS supplied information, to determine
> +		 * the topology.
> +		 */

Egads.. do we realy have to trust BIOS data? BIOS crud tends to be
bonghits qualitee :/

> +		if (nr_node_ids <= 8) {
> +			/* get the Node ID of the local register */
> +			err = pci_read_config_dword(ubox_dev, nodeid_loc, &config);
> +			if (err)
> +				break;
> +			nodeid = config & NODE_ID_MASK;
> +			/* get the Node ID mapping */
> +			err = pci_read_config_dword(ubox_dev, idmap_loc, &config);
> +			if (err)
> +				break;
>  
> +			segment = pci_domain_nr(ubox_dev->bus);
> +			raw_spin_lock(&pci2phy_map_lock);
> +			map = __find_pci2phy_map(segment);
> +			if (!map) {
> +				raw_spin_unlock(&pci2phy_map_lock);
> +				err = -ENOMEM;
> +				break;
> +			}
> +
> +			/*
> +			 * every three bits in the Node ID mapping register maps
> +			 * to a particular node.
> +			 */
> +			for (i = 0; i < 8; i++) {
> +				if (nodeid == ((config >> (3 * i)) & 0x7)) {
> +					if (topology_max_die_per_package() > 1)
> +						die_id = i;
> +					else
> +						die_id = topology_phys_to_logical_pkg(i);
> +					map->pbus_to_dieid[bus] = die_id;
> +					break;
> +				}
> +			}
>  			raw_spin_unlock(&pci2phy_map_lock);
> +		} else {
> +			int node = pcibus_to_node(ubox_dev->bus);
> +			int cpu;
> +
> +			segment = pci_domain_nr(ubox_dev->bus);
> +			raw_spin_lock(&pci2phy_map_lock);
> +			map = __find_pci2phy_map(segment);
> +			if (!map) {
> +				raw_spin_unlock(&pci2phy_map_lock);
> +				err = -ENOMEM;
> +				break;
> +			}
> +			die_id = -1;
> +			for_each_cpu(cpu, cpumask_of_pcibus(ubox_dev->bus)) {
> +				struct cpuinfo_x86 *c = &cpu_data(cpu);
> +
> +				if (c->initialized && cpu_to_node(cpu) == node) {
> +					map->pbus_to_dieid[bus] = die_id = c->logical_die_id;
> +					break;
> +				}
> +			}
> +			raw_spin_unlock(&pci2phy_map_lock);
> +
> +			if (WARN_ON_ONCE(die_id == -1)) {
> +				err = -EINVAL;
>  				break;
>  			}

This seems to assume a single die per node; is that fundemantally
correct?

Did you consider malicious BIOS data? I think we're good, but I didn't
look too hard.

>  		}
>  	}
>  
>  	if (!err) {
> -- 
> 2.26.2
>