linux-kernel - Re: [PATCH V2 03/13] perf/x86/intel/uncore: Remove has_generic_discovery

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Message-ID: <2a33e952-db37-43f3-943c-545360c3b682@linux.intel.com>
Date: Sun, 4 Jan 2026 10:03:16 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Zide Chen <zide.chen@...el.com>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Andi Kleen <ak@...ux.intel.com>, Eranian Stephane <eranian@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Xudong Hao <xudong.hao@...el.com>, Falcon Thomas <thomas.falcon@...el.com>
Subject: Re: [PATCH V2 03/13] perf/x86/intel/uncore: Remove
 has_generic_discovery_table()


On 1/1/2026 6:42 AM, Zide Chen wrote:
> In the !x86_match_cpu() fallback path, has_generic_discovery_table()
> is removed because it does not handle multiple PCI devices.  Instead,
> use PCI_ANY_ID in generic_uncore_init[] to probe all PCI devices.
>
> For MSR portals, only probe MSR 0x201e to keep the fallback simple, as
> this path is best-effort only.
>
> Signed-off-by: Zide Chen <zide.chen@...el.com>
> ---
> V2: Separate patch from [PATCH V1 1/7]
> - Move has_generic_discovery_table() related code to its own patch for
>   easier review.
>
>  arch/x86/events/intel/uncore.c           |  3 ++
>  arch/x86/events/intel/uncore_discovery.c | 42 +++++-------------------
>  2 files changed, 12 insertions(+), 33 deletions(-)
>
> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
> index 844030ef87c4..2a1c6dce8a35 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -1835,6 +1835,9 @@ static const struct uncore_plat_init generic_uncore_init __initconst = {
>  	.cpu_init = intel_uncore_generic_uncore_cpu_init,
>  	.pci_init = intel_uncore_generic_uncore_pci_init,
>  	.mmio_init = intel_uncore_generic_uncore_mmio_init,
> +	.domain[0].base_is_pci = true,
> +	.domain[0].discovery_base = PCI_ANY_ID,
> +	.domain[1].discovery_base = UNCORE_DISCOVERY_MSR,
>  };
>  
>  static const struct x86_cpu_id intel_uncore_match[] __initconst = {
> diff --git a/arch/x86/events/intel/uncore_discovery.c b/arch/x86/events/intel/uncore_discovery.c
> index 3bcbf974d3a8..6f409e0b4722 100644
> --- a/arch/x86/events/intel/uncore_discovery.c
> +++ b/arch/x86/events/intel/uncore_discovery.c
> @@ -12,24 +12,6 @@
>  static struct rb_root discovery_tables = RB_ROOT;
>  static int num_discovered_types[UNCORE_ACCESS_MAX];
>  
> -static bool has_generic_discovery_table(void)
> -{
> -	struct pci_dev *dev;
> -	int dvsec;
> -
> -	dev = pci_get_device(PCI_VENDOR_ID_INTEL, UNCORE_DISCOVERY_TABLE_DEVICE, NULL);
> -	if (!dev)
> -		return false;
> -
> -	/* A discovery table device has the unique capability ID. */
> -	dvsec = pci_find_next_ext_capability(dev, 0, UNCORE_EXT_CAP_ID_DISCOVERY);
> -	pci_dev_put(dev);
> -	if (dvsec)
> -		return true;
> -
> -	return false;
> -}
> -
>  static int logical_die_id;
>  
>  static int get_device_die_id(struct pci_dev *dev)
> @@ -358,12 +340,7 @@ static bool uncore_discovery_pci(struct uncore_discovery_domain *domain)
>  	struct pci_dev *dev = NULL;
>  	bool parsed = false;
>  
> -	if (domain->discovery_base)
> -		device = domain->discovery_base;
> -	else if (has_generic_discovery_table())
> -		device = UNCORE_DISCOVERY_TABLE_DEVICE;
> -	else
> -		device = PCI_ANY_ID;
> +	device = domain->discovery_base;
>  
>  	/*
>  	 * Start a new search and iterates through the list of
> @@ -406,7 +383,7 @@ static bool uncore_discovery_msr(struct uncore_discovery_domain *domain)
>  {
>  	unsigned long *die_mask;
>  	bool parsed = false;
> -	int cpu, die, msr;
> +	int cpu, die;
>  	u64 base;
>  
>  	die_mask = kcalloc(BITS_TO_LONGS(uncore_max_dies()),
> @@ -414,16 +391,13 @@ static bool uncore_discovery_msr(struct uncore_discovery_domain *domain)
>  	if (!die_mask)
>  		return false;
>  
> -	msr = domain->discovery_base ?
> -	      domain->discovery_base : UNCORE_DISCOVERY_MSR;
> -
>  	cpus_read_lock();
>  	for_each_online_cpu(cpu) {
>  		die = topology_logical_die_id(cpu);
>  		if (__test_and_set_bit(die, die_mask))
>  			continue;
>  
> -		if (rdmsrq_safe_on_cpu(cpu, msr, &base))
> +		if (rdmsrq_safe_on_cpu(cpu, domain->discovery_base, &base))
>  			continue;
>  
>  		if (!base)
> @@ -446,10 +420,12 @@ bool uncore_discovery(struct uncore_plat_init *init)
>  
>  	for (i = 0; i < UNCORE_DISCOVERY_DOMAINS; i++) {
>  		domain = &init->domain[i];
> -		if (!domain->base_is_pci)
> -			ret |= uncore_discovery_msr(domain);
> -		else
> -			ret |= uncore_discovery_pci(domain);
> +		if (domain->discovery_base) {
> +			if (!domain->base_is_pci)
> +				ret |= uncore_discovery_msr(domain);
> +			else
> +				ret |= uncore_discovery_pci(domain);
> +		}
>  	}
>  
>  	return ret;

LGTM. 

Reviewed-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>