Merge tag 'x86-urgent-2023-10-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull misc x86 fixes from Ingo Molnar:

 - Fix a possible CPU hotplug deadlock bug caused by the new TSC
   synchronization code

 - Fix a legacy PIC discovery bug that results in device troubles on
   affected systems, such as non-working keybards, etc

 - Add a new Intel CPU model number to <asm/intel-family.h>

* tag 'x86-urgent-2023-10-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/tsc: Defer marking TSC unstable to a worker
  x86/i8259: Skip probing when ACPI/MADT advertises PCAT compatibility
  x86/cpu: Add model number for Intel Arrow Lake mobile processor

Author: torvalds

arch/x86/include/asm/i8259.h

@@ -69,6 +69,8 @@ struct legacy_pic {
 	void (*make_irq)(unsigned int irq);
 };
 
+void legacy_pic_pcat_compat(void);
+
 extern struct legacy_pic *legacy_pic;
 extern struct legacy_pic null_legacy_pic;
 

arch/x86/include/asm/intel-family.h

@@ -27,6 +27,7 @@
  *		_X	- regular server parts
  *		_D	- micro server parts
  *		_N,_P	- other mobile parts
+ *		_H	- premium mobile parts
  *		_S	- other client parts
  *
  *		Historical OPTDIFFs:
@@ -124,6 +125,7 @@
 #define INTEL_FAM6_METEORLAKE		0xAC
 #define INTEL_FAM6_METEORLAKE_L		0xAA
 
+#define INTEL_FAM6_ARROWLAKE_H		0xC5
 #define INTEL_FAM6_ARROWLAKE		0xC6
 
 #define INTEL_FAM6_LUNARLAKE_M		0xBD

arch/x86/kernel/acpi/boot.c

@@ -148,6 +148,9 @@ static int __init acpi_parse_madt(struct acpi_table_header *table)
 		pr_debug("Local APIC address 0x%08x\n", madt->address);
 	}
 
+	if (madt->flags & ACPI_MADT_PCAT_COMPAT)
+		legacy_pic_pcat_compat();
+
 	/* ACPI 6.3 and newer support the online capable bit. */
 	if (acpi_gbl_FADT.header.revision > 6 ||
 	    (acpi_gbl_FADT.header.revision == 6 &&

arch/x86/kernel/i8259.c

@@ -32,6 +32,7 @@
  */
 static void init_8259A(int auto_eoi);
 
+static bool pcat_compat __ro_after_init;
 static int i8259A_auto_eoi;
 DEFINE_RAW_SPINLOCK(i8259A_lock);
 
@@ -299,15 +300,32 @@ static void unmask_8259A(void)
 
 static int probe_8259A(void)
 {
+	unsigned char new_val, probe_val = ~(1 << PIC_CASCADE_IR);
 	unsigned long flags;
-	unsigned char probe_val = ~(1 << PIC_CASCADE_IR);
-	unsigned char new_val;
+
+	/*
+	 * If MADT has the PCAT_COMPAT flag set, then do not bother probing
+	 * for the PIC. Some BIOSes leave the PIC uninitialized and probing
+	 * fails.
+	 *
+	 * Right now this causes problems as quite some code depends on
+	 * nr_legacy_irqs() > 0 or has_legacy_pic() == true. This is silly
+	 * when the system has an IO/APIC because then PIC is not required
+	 * at all, except for really old machines where the timer interrupt
+	 * must be routed through the PIC. So just pretend that the PIC is
+	 * there and let legacy_pic->init() initialize it for nothing.
+	 *
+	 * Alternatively this could just try to initialize the PIC and
+	 * repeat the probe, but for cases where there is no PIC that's
+	 * just pointless.
+	 */
+	if (pcat_compat)
+		return nr_legacy_irqs();
+
 	/*
-	 * Check to see if we have a PIC.
-	 * Mask all except the cascade and read
-	 * back the value we just wrote. If we don't
-	 * have a PIC, we will read 0xff as opposed to the
-	 * value we wrote.
+	 * Check to see if we have a PIC.  Mask all except the cascade and
+	 * read back the value we just wrote. If we don't have a PIC, we
+	 * will read 0xff as opposed to the value we wrote.
 	 */
 	raw_spin_lock_irqsave(&i8259A_lock, flags);
 
@@ -429,5 +447,9 @@ static int __init i8259A_init_ops(void)
 
 	return 0;
 }
-
 device_initcall(i8259A_init_ops);
+
+void __init legacy_pic_pcat_compat(void)
+{
+	pcat_compat = true;
+}

arch/x86/kernel/tsc_sync.c

@@ -15,6 +15,7 @@
  * ( The serial nature of the boot logic and the CPU hotplug lock
  *   protects against more than 2 CPUs entering this code. )
  */
+#include <linux/workqueue.h>
 #include <linux/topology.h>
 #include <linux/spinlock.h>
 #include <linux/kernel.h>
@@ -342,6 +343,13 @@ static inline unsigned int loop_timeout(int cpu)
 	return (cpumask_weight(topology_core_cpumask(cpu)) > 1) ? 2 : 20;
 }
 
+static void tsc_sync_mark_tsc_unstable(struct work_struct *work)
+{
+	mark_tsc_unstable("check_tsc_sync_source failed");
+}
+
+static DECLARE_WORK(tsc_sync_work, tsc_sync_mark_tsc_unstable);
+
 /*
  * The freshly booted CPU initiates this via an async SMP function call.
  */
@@ -395,7 +403,7 @@ static void check_tsc_sync_source(void *__cpu)
 			"turning off TSC clock.\n", max_warp);
 		if (random_warps)
 			pr_warn("TSC warped randomly between CPUs\n");
-		mark_tsc_unstable("check_tsc_sync_source failed");
+		schedule_work(&tsc_sync_work);
 	}
 
 	/*