[tip: x86/apic] x86/apic: Sanitize num_processors handling

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/apic branch of tip:

Commit-ID:     e8122513ff9e92cdc514ad6cbb5c25d551ac3629
Gitweb:        https://git.kernel.org/tip/e8122513ff9e92cdc514ad6cbb5c25d551ac3629
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Tue, 08 Aug 2023 15:03:50 -07:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Wed, 09 Aug 2023 11:58:21 -07:00

x86/apic: Sanitize num_processors handling

num_processors is 0 by default and only gets incremented when local APICs
are registered.

Make init_apic_mappings(), which tries to enable the local APIC in the case
that no SMP configuration was found set num_processors to 1.

This allows to remove yet another check for the local APIC and yet another
place which registers the boot CPUs local APIC ID.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Tested-by: Sohil Mehta <sohil.mehta@xxxxxxxxx>
Tested-by: Juergen Gross <jgross@xxxxxxxx> # Xen PV (dom0 and unpriv. guest)
---
 arch/x86/kernel/apic/apic.c |  9 ++++++---
 arch/x86/kernel/smpboot.c   | 18 ------------------
 2 files changed, 6 insertions(+), 21 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 84ff5b2..564d584 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2130,9 +2130,12 @@ void __init init_apic_mappings(void)
 	if (x2apic_mode)
 		return;
 
-	if (!smp_found_config && !detect_init_APIC()) {
-		pr_info("APIC: disable apic facility\n");
-		apic_disable();
+	if (!smp_found_config) {
+		if (!detect_init_APIC()) {
+			pr_info("APIC: disable apic facility\n");
+			apic_disable();
+		}
+		num_processors = 1;
 	}
 }
 
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 5467c58..fc2173b 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1397,24 +1397,6 @@ __init void prefill_possible_map(void)
 {
 	int i, possible;
 
-	/* No processor was found in mptable or ACPI MADT */
-	if (!num_processors) {
-		if (boot_cpu_has(X86_FEATURE_APIC)) {
-			int apicid = boot_cpu_physical_apicid;
-			int cpu = read_apic_id();
-
-			pr_warn("Boot CPU (id %d) not listed by BIOS\n", cpu);
-
-			/* Make sure boot cpu is enumerated */
-			if (apic->cpu_present_to_apicid(0) == BAD_APICID &&
-			    apic->apic_id_valid(apicid))
-				generic_processor_info(apicid);
-		}
-
-		if (!num_processors)
-			num_processors = 1;
-	}
-
 	i = setup_max_cpus ?: 1;
 	if (setup_possible_cpus == -1) {
 		possible = num_processors;