Change in coreboot[master]: cpu/x86/lapic: Unconditionally use CPUID leaf 0xb if available

[Kyösti Mälkki (Code Review)]

Kyösti Mälkki has submitted this change. ( https://review.coreboot.org/c/coreboot/+/58386 )

Change subject: cpu/x86/lapic: Unconditionally use CPUID leaf 0xb if available
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cpu/x86/lapic: Unconditionally use CPUID leaf 0xb if available

Even when we're not in X2APIC mode, the information in CPUID
leaf 0xb will be valid if that leaf is implemented on the CPU.

Change-Id: I0f1f46fe5091ebeab6dfb4c7e151150cf495d0cb
Signed-off-by: Kyösti Mälkki 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58386
Tested-by: build bot (Jenkins) 
Reviewed-by: Tim Wawrzynczak 
Reviewed-by: Wonkyu Kim 
Reviewed-by: Arthur Heymans 
Reviewed-by: Angel Pons 
---
M src/cpu/x86/smm/smm_stub.S
M src/include/cpu/x86/lapic.h
2 files changed, 8 insertions(+), 13 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Arthur Heymans: Looks good to me, approved
  Angel Pons: Looks good to me, but someone else must approve
  Wonkyu Kim: Looks good to me, but someone else must approve
  Tim Wawrzynczak: Looks good to me, but someone else must approve

diff --git a/src/cpu/x86/smm/smm_stub.S b/src/cpu/x86/smm/smm_stub.S
index c83839c..25a35aa 100644
--- a/src/cpu/x86/smm/smm_stub.S
+++ b/src/cpu/x86/smm/smm_stub.S
@@ -101,30 +101,25 @@
     * the OS can manipulate the APIC id use the non-changing cpuid result
     * for APIC id (eax). A table is used to handle a discontiguous
     * APIC id space.  */
-apic_id:
-	mov	$LAPIC_BASE_MSR, %ecx
-	rdmsr
-	and	$LAPIC_BASE_X2APIC_ENABLED, %eax
-	cmp	$LAPIC_BASE_X2APIC_ENABLED, %eax
-	jne	xapic

-x2apic:
+	mov	$0, %eax
+	cpuid
+	cmp	$0xb, %eax
+	jc	1f
    mov	$0xb, %eax
    mov	$0, %ecx
    cpuid
    mov	%edx, %eax
-	jmp	apicid_end
-
-xapic:
+	jmp	2f
+1:
    mov	$1, %eax
    cpuid
    mov	%ebx, %eax
    shr	$24, %eax
+2:

-apicid_end:
    mov	$(apic_to_cpu_num), %ebx
    xor	%ecx, %ecx
-
 1:
    cmp	(%ebx, %ecx, 2), %ax
    je	1f
diff --git a/src/include/cpu/x86/lapic.h b/src/include/cpu/x86/lapic.h
index 05d096e..537fa97 100644
--- a/src/include/cpu/x86/lapic.h
+++ b/src/include/cpu/x86/lapic.h
@@ -126,7 +126,7 @@
 static __always_inline unsigned int initial_lapicid(void)
 {
    uint32_t lapicid;
-	if (is_x2apic_mode() && cpuid_get_max_func() >= 0xb)
+	if (cpuid_get_max_func() >= 0xb)
    	lapicid = cpuid_ext(0xb, 0).edx;
    else
    	lapicid = cpuid_ebx(1) >> 24;