x86/cpu: Provide cpu_init/parse_topology()

Topology evaluation is a complete disaster and impenetrable mess. It's
scattered all over the place with some vendor implementations doing early
evaluation and some not. The most horrific part is the permanent
overwriting of smt_max_siblings and __max_die_per_package, instead of
establishing them once on the boot CPU and validating the result on the
APs.

The goals are:

  - One topology evaluation entry point

  - Proper sharing of pointlessly duplicated code

  - Proper structuring of the evaluation logic and preferences.

  - Evaluating important system wide information only once on the boot CPU

  - Making the 0xb/0x1f leaf parsing less convoluted and actually fixing
    the short comings of leaf 0x1f evaluation.

Start to consolidate the topology evaluation code by providing the entry
points for the early boot CPU evaluation and for the final parsing on the
boot CPU and the APs.

Move the trivial pieces into that new code:

   - The initialization of cpuinfo_x86::topo

   - The evaluation of CPUID leaf 1, which presets topo::initial_apicid

   - topo_apicid is set to topo::initial_apicid when invoked from early
     boot. When invoked for the final evaluation on the boot CPU it reads
     the actual APIC ID, which makes apic_get_initial_apicid() obsolete
     once everything is converted over.

Provide a temporary helper function topo_converted() which shields off the
not yet converted CPU vendors from invoking code which would break them.
This shielding covers all vendor CPUs which support SMP, but not the
historical pure UP ones as they only need the topology info init and
eventually the initial APIC initialization.

Provide two new members in cpuinfo_x86::topo to store the maximum number of
SMT siblings and the number of dies per package and add them to the debugfs
readout. These two members will be used to populate this information on the
boot CPU and to validate the APs against it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juergen Gross <jgross@suse.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Tested-by: Wang Wendy <wendy.wang@intel.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240212153624.581436579@linutronix.de

1 files changed, 36 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/topology.h b/arch/x86/kernel/cpu/topology.h
new file mode 100644
index 000000000000..99c94c519b5d
--- /dev/null
+++ b/arch/x86/kernel/cpu/topology.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef ARCH_X86_TOPOLOGY_H
+#define ARCH_X86_TOPOLOGY_H
+
+struct topo_scan {
+	struct cpuinfo_x86	*c;
+	unsigned int		dom_shifts[TOPO_MAX_DOMAIN];
+	unsigned int		dom_ncpus[TOPO_MAX_DOMAIN];
+};
+
+bool topo_is_converted(struct cpuinfo_x86 *c);
+void cpu_init_topology(struct cpuinfo_x86 *c);
+void cpu_parse_topology(struct cpuinfo_x86 *c);
+void topology_set_dom(struct topo_scan *tscan, enum x86_topology_domains dom,
+		      unsigned int shift, unsigned int ncpus);
+
+static inline u32 topo_shift_apicid(u32 apicid, enum x86_topology_domains dom)
+{
+	if (dom == TOPO_SMT_DOMAIN)
+		return apicid;
+	return apicid >> x86_topo_system.dom_shifts[dom - 1];
+}
+
+static inline u32 topo_relative_domain_id(u32 apicid, enum x86_topology_domains dom)
+{
+	if (dom != TOPO_SMT_DOMAIN)
+		apicid >>= x86_topo_system.dom_shifts[dom - 1];
+	return apicid & (x86_topo_system.dom_size[dom] - 1);
+}
+
+static inline u32 topo_domain_mask(enum x86_topology_domains dom)
+{
+	return (1U << x86_topo_system.dom_shifts[dom]) - 1;
+}
+
+#endif /* ARCH_X86_TOPOLOGY_H */