[PATCH v2 gnumach] apic: Set up LAPICs in xAPIC mode

[Damien Zammit]

Clear flag in msr for xAPIC mode.

---
 i386/i386/apic.h      | 3 ++-
 i386/i386/cpuboot.S   | 4 ++--
 i386/i386at/boothdr.S | 3 ++-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/i386/i386/apic.h b/i386/i386/apic.h
index b8fff2af..e410e9c6 100644
--- a/i386/i386/apic.h
+++ b/i386/i386/apic.h
@@ -302,7 +302,8 @@ extern int cpu_id_lut[];
 
 #define APIC_MSR                       0x1b
 #define APIC_MSR_BSP                   0x100 /* Processor is a BSP */
-#define APIC_MSR_ENABLE                0x800
+#define APIC_MSR_X2APIC                0x400 /* LAPIC is in x2APIC mode */
+#define APIC_MSR_ENABLE                0x800 /* LAPIC is enabled */
 
 /* Set or clear a bit in a 255-bit APIC mask register.
    These registers are spread through eight 32-bit registers.  */
diff --git a/i386/i386/cpuboot.S b/i386/i386/cpuboot.S
index c85c4ddb..13d9160e 100644
--- a/i386/i386/cpuboot.S
+++ b/i386/i386/cpuboot.S
@@ -175,13 +175,13 @@ _apboot:
        mov     apboot_idt_ptr, %ebx
        lidt    (%ebx)
 
-       /* Enable local apic */
+       /* Enable local apic in xAPIC mode */
        xorl    %eax, %eax
        xorl    %edx, %edx
        movl    $APIC_MSR, %ecx
        rdmsr
        orl     $APIC_MSR_ENABLE, %eax
-       andl    $(~APIC_MSR_BSP), %eax
+       andl    $(~(APIC_MSR_BSP | APIC_MSR_X2APIC)), %eax
        movl    $APIC_MSR, %ecx
        wrmsr
 
diff --git a/i386/i386at/boothdr.S b/i386/i386at/boothdr.S
index 6696d966..daaf57db 100644
--- a/i386/i386at/boothdr.S
+++ b/i386/i386at/boothdr.S
@@ -67,13 +67,14 @@ boot_entry:
        movl    $solid_intstack+INTSTACK_SIZE-4, %esp
        andl    $0xfffffff0,%esp
 
-       /* Enable local apic */
+       /* Enable local apic in xAPIC mode */
        xorl    %eax, %eax
        xorl    %edx, %edx
        movl    $APIC_MSR, %ecx
        rdmsr
        orl     $APIC_MSR_ENABLE, %eax
        orl     $APIC_MSR_BSP, %eax
+       andl    $(~APIC_MSR_X2APIC), %eax
        movl    $APIC_MSR, %ecx
        wrmsr
 
-- 
2.43.0