[PATCH] x86: read apic id if it is not acpi_lapic

[Yinghai Lu]

Ed found that on 32bit, boot_cpu_physical_apicid is not read right,
when mptable is broken.

interesting, actually three path
1. acpi: at that time, at that time that is already read from reg.
2. mptable: that only read from mptable.
3. no madt, and no mptable, that use default apic id 0 for 64bit, -1 for 32bit

so could read that apic id for 2/3 path.

also could avoid set fixmap that lapic two times when acpi_lapic is used.
and need to move cpu_has_apic earlier and call apic_disable()

Reported-by: Ed Swierk <eswierk@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>

---
 arch/x86/kernel/apic/apic.c |   29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/apic.c
+++ linux-2.6/arch/x86/kernel/apic/apic.c
@@ -1574,6 +1574,8 @@ void __init early_init_lapic_mapping(voi
  */
 void __init init_apic_mappings(void)
 {
+	unsigned int new_apicid;
+
 	if (x2apic_mode) {
 		boot_cpu_physical_apicid = read_apic_id();
 		return;
@@ -1590,21 +1592,32 @@ void __init init_apic_mappings(void)
 	} else
 		apic_phys = mp_lapic_addr;
 
-	set_fixmap_nocache(FIX_APIC_BASE, apic_phys);
+	/* lets check if we may to NOP'ify apic operations */
+	if (!cpu_has_apic) {
+		pr_info("APIC: disable apic facility\n");
+		apic_disable();
+		return;
+	}
+
+	/*
+	 * acpi lapic path already map that address in
+	 * acpi_register_lapic_address()
+	 */
 	apic_printk(APIC_VERBOSE, "mapped APIC to %08lx (%08lx)\n",
 				APIC_BASE, apic_phys);
+	if (acpi_lapic)
+		return;
 
+	set_fixmap_nocache(FIX_APIC_BASE, apic_phys);
 	/*
 	 * Fetch the APIC ID of the BSP in case we have a
 	 * default configuration (or the MP table is broken).
 	 */
-	if (boot_cpu_physical_apicid == -1U)
-		boot_cpu_physical_apicid = read_apic_id();
-
-	/* lets check if we may to NOP'ify apic operations */
-	if (!cpu_has_apic) {
-		pr_info("APIC: disable apic facility\n");
-		apic_disable();
+	new_apicid  = read_apic_id();
+	if (boot_cpu_physical_apicid != new_apicid) {
+		boot_cpu_physical_apicid  = new_apicid;
+		apic_version[new_apicid] =
+			 GET_APIC_VERSION(apic_read(APIC_LVR));
 	}
 }
 
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