Merge tag 'x86-apic-2022-12-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 apic update from Thomas Gleixner:
 "A set of changes for the x86 APIC code:

   - Handle the case where x2APIC is enabled and locked by the BIOS on a
     kernel with CONFIG_X86_X2APIC=n gracefully.

     Instead of a panic which does not make it to the graphical console
     during very early boot, simply disable the local APIC completely
     and boot with the PIC and very limited functionality, which allows
     to diagnose the issue

   - Convert x86 APIC device tree bindings to YAML

   - Extend x86 APIC device tree bindings to configure interrupt
     delivery mode and handle this in during init. This allows to boot
     with device tree on platforms which lack a legacy PIC"

* tag 'x86-apic-2022-12-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/of: Add support for boot time interrupt delivery mode configuration
  x86/of: Replace printk(KERN_LVL) with pr_lvl()
  dt-bindings: x86: apic: Introduce new optional bool property for lapic
  dt-bindings: x86: apic: Convert Intel's APIC bindings to YAML schema
  x86/of: Remove unused early_init_dt_add_memory_arch()
  x86/apic: Handle no CONFIG_X86_X2APIC on systems with x2APIC enabled by BIOS

4 files changed, 21 insertions, 17 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e2eebb193ee0..68a2a04c02e5 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -463,8 +463,8 @@ config X86_X2APIC
 
 	  Some Intel systems circa 2022 and later are locked into x2APIC mode
 	  and can not fall back to the legacy APIC modes if SGX or TDX are
-	  enabled in the BIOS.  They will be unable to boot without enabling
-	  this option.
+	  enabled in the BIOS. They will boot with very reduced functionality
+	  without enabling this option.
 
 	  If you don't know what to do here, say N.
 
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 3415321c8240..3216da7074ba 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -249,7 +249,6 @@ static inline u64 native_x2apic_icr_read(void)
 extern int x2apic_mode;
 extern int x2apic_phys;
 extern void __init x2apic_set_max_apicid(u32 apicid);
-extern void __init check_x2apic(void);
 extern void x2apic_setup(void);
 static inline int x2apic_enabled(void)
 {
@@ -258,13 +257,13 @@ static inline int x2apic_enabled(void)
 
 #define x2apic_supported()	(boot_cpu_has(X86_FEATURE_X2APIC))
 #else /* !CONFIG_X86_X2APIC */
-static inline void check_x2apic(void) { }
 static inline void x2apic_setup(void) { }
 static inline int x2apic_enabled(void) { return 0; }
 
 #define x2apic_mode		(0)
 #define	x2apic_supported()	(0)
 #endif /* !CONFIG_X86_X2APIC */
+extern void __init check_x2apic(void);
 
 struct irq_data;
 
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index c6876d3ea4b1..20d9a604da7c 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1931,16 +1931,19 @@ void __init check_x2apic(void)
 	}
 }
 #else /* CONFIG_X86_X2APIC */
-static int __init validate_x2apic(void)
+void __init check_x2apic(void)
 {
 	if (!apic_is_x2apic_enabled())
-		return 0;
+		return;
 	/*
-	 * Checkme: Can we simply turn off x2apic here instead of panic?
+	 * Checkme: Can we simply turn off x2APIC here instead of disabling the APIC?
 	 */
-	panic("BIOS has enabled x2apic but kernel doesn't support x2apic, please disable x2apic in BIOS.\n");
+	pr_err("Kernel does not support x2APIC, please recompile with CONFIG_X86_X2APIC.\n");
+	pr_err("Disabling APIC, expect reduced performance and functionality.\n");
+
+	disable_apic = 1;
+	setup_clear_cpu_cap(X86_FEATURE_APIC);
 }
-early_initcall(validate_x2apic);
 
 static inline void try_to_enable_x2apic(int remap_mode) { }
 static inline void __x2apic_enable(void) { }
diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
index 5cd51f25f446..28da5dd83fc0 100644
--- a/arch/x86/kernel/devicetree.c
+++ b/arch/x86/kernel/devicetree.c
@@ -31,11 +31,6 @@ char __initdata cmd_line[COMMAND_LINE_SIZE];
 
 int __initdata of_ioapic;
 
-void __init early_init_dt_add_memory_arch(u64 base, u64 size)
-{
-	BUG();
-}
-
 void __init add_dtb(u64 data)
 {
 	initial_dtb = data + offsetof(struct setup_data, data);
@@ -167,7 +162,14 @@ static void __init dtb_lapic_setup(void)
 			return;
 	}
 	smp_found_config = 1;
-	pic_mode = 1;
+	if (of_property_read_bool(dn, "intel,virtual-wire-mode")) {
+		pr_info("Virtual Wire compatibility mode.\n");
+		pic_mode = 0;
+	} else {
+		pr_info("IMCR and PIC compatibility mode.\n");
+		pic_mode = 1;
+	}
+
 	register_lapic_address(lapic_addr);
 }
 
@@ -248,7 +250,7 @@ static void __init dtb_add_ioapic(struct device_node *dn)
 
 	ret = of_address_to_resource(dn, 0, &r);
 	if (ret) {
-		printk(KERN_ERR "Can't obtain address from device node %pOF.\n", dn);
+		pr_err("Can't obtain address from device node %pOF.\n", dn);
 		return;
 	}
 	mp_register_ioapic(++ioapic_id, r.start, gsi_top, &cfg);
@@ -265,7 +267,7 @@ static void __init dtb_ioapic_setup(void)
 		of_ioapic = 1;
 		return;
 	}
-	printk(KERN_ERR "Error: No information about IO-APIC in OF.\n");
+	pr_err("Error: No information about IO-APIC in OF.\n");
 }
 #else
 static void __init dtb_ioapic_setup(void) {}