linux-kernel - [patch v2 18/38] x86/cpu/topology: Cure the abuse of cpuinfo for persisting logical ids

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Message-ID: <20230728120930.672330175@linutronix.de>
Date:   Fri, 28 Jul 2023 14:13:05 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Tom Lendacky <thomas.lendacky@....com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Dick Kennedy <dick.kennedy@...adcom.com>,
        James Smart <james.smart@...adcom.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        linux-hwmon@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
        Huang Rui <ray.huang@....com>, Juergen Gross <jgross@...e.com>,
        Steve Wahl <steve.wahl@....com>,
        Mike Travis <mike.travis@....com>,
        Dimitri Sivanich <dimitri.sivanich@....com>,
        Russ Anderson <russ.anderson@....com>
Subject: [patch v2 18/38] x86/cpu/topology: Cure the abuse of cpuinfo for
 persisting logical ids

Per CPU cpuinfo is used to persist the logical package and die IDs. That's
really not the right place simply because cpuinfo is subject to be
reinitialized when a CPU goes through an offline/online cycle.

This works by chance today, but that's far from correct and neither obvious
nor documented.

Add a per cpu datastructure which persists those logical IDs, which allows
to cleanup the CPUID evaluation code.

This is a temporary workaround until the larger topology management is in
place, which makes all of this logical management mechanics obsolete.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/smpboot.c |   33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -124,7 +124,20 @@ struct mwait_cpu_dead {
  */
 static DEFINE_PER_CPU_ALIGNED(struct mwait_cpu_dead, mwait_cpu_dead);
 
-/* Logical package management. We might want to allocate that dynamically */
+/* Logical package management. */
+struct logical_maps {
+	u32	phys_pkg_id;
+	u32	phys_die_id;
+	u32	logical_pkg_id;
+	u32	logical_die_id;
+};
+
+/* Temporary workaround until the full topology mechanics is in place */
+static DEFINE_PER_CPU_READ_MOSTLY(struct logical_maps, logical_maps) = {
+	.phys_pkg_id	= U32_MAX,
+	.phys_die_id	= U32_MAX,
+};
+
 unsigned int __max_logical_packages __read_mostly;
 EXPORT_SYMBOL(__max_logical_packages);
 static unsigned int logical_packages __read_mostly;
@@ -345,10 +358,8 @@ int topology_phys_to_logical_pkg(unsigne
 	int cpu;
 
 	for_each_possible_cpu(cpu) {
-		struct cpuinfo_x86 *c = &cpu_data(cpu);
-
-		if (c->initialized && c->topo.pkg_id == phys_pkg)
-			return c->topo.logical_pkg_id;
+		if (per_cpu(logical_maps.phys_pkg_id, cpu) == phys_pkg)
+			return per_cpu(logical_maps.logical_pkg_id, cpu);
 	}
 	return -1;
 }
@@ -366,11 +377,9 @@ static int topology_phys_to_logical_die(
 	int cpu, proc_id = cpu_data(cur_cpu).topo.pkg_id;
 
 	for_each_possible_cpu(cpu) {
-		struct cpuinfo_x86 *c = &cpu_data(cpu);
-
-		if (c->initialized && c->topo.die_id == die_id &&
-		    c->topo.pkg_id == proc_id)
-			return c->topo.logical_die_id;
+		if (per_cpu(logical_maps.phys_pkg_id, cpu) == proc_id &&
+		    per_cpu(logical_maps.phys_die_id, cpu) == die_id)
+			return per_cpu(logical_maps.logical_die_id, cpu);
 	}
 	return -1;
 }
@@ -395,6 +404,8 @@ int topology_update_package_map(unsigned
 			cpu, pkg, new);
 	}
 found:
+	per_cpu(logical_maps.phys_pkg_id, cpu) = pkg;
+	per_cpu(logical_maps.logical_pkg_id, cpu) = new;
 	cpu_data(cpu).topo.logical_pkg_id = new;
 	return 0;
 }
@@ -418,6 +429,8 @@ int topology_update_die_map(unsigned int
 			cpu, die, new);
 	}
 found:
+	per_cpu(logical_maps.phys_die_id, cpu) = die;
+	per_cpu(logical_maps.logical_die_id, cpu) = new;
 	cpu_data(cpu).topo.logical_die_id = new;
 	return 0;
 }