Change in coreboot[master]: [WIP] cpu/x86: Add Kconfig X2APIC SUPPORT

[Kyösti Mälkki (Code Review)]

Kyösti Mälkki has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/55073 )

Change subject: [WIP] cpu/x86: Add Kconfig X2APIC_SUPPORT
......................................................................

[WIP] cpu/x86: Add Kconfig X2APIC_SUPPORT

Allows compile-time optimisation on platforms that do not wish
to enable runtime checking of X2APIC_ENABLED.

Legacy lapic_cpu_init() is incompatible so there is dependency
on PARALLEL_MP. Also stop_this_cpu() is incompatible, so there
is dependency on !AP_IN_SIPI_WAIT.

Change-Id: I8269f9639ee3e89a2c2b4178d266ba2dac46db3f
Signed-off-by: Kyösti Mälkki 
---
M src/cpu/x86/Kconfig
M src/include/cpu/x86/lapic.h
2 files changed, 10 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/73/55073/1

diff --git a/src/cpu/x86/Kconfig b/src/cpu/x86/Kconfig
index bcaf0bf..ad53229 100644
--- a/src/cpu/x86/Kconfig
+++ b/src/cpu/x86/Kconfig
@@ -17,6 +17,13 @@
     Allow APs to do other work after initialization instead of going
     to sleep.

+config X2APIC_SUPPORT
+	bool
+	depends on PARALLEL_MP
+	depends on !AP_IN_SIPI_WAIT
+	help
+	 Add support for X2_APIC mode.
+
 config UDELAY_LAPIC
    bool
    default n
diff --git a/src/include/cpu/x86/lapic.h b/src/include/cpu/x86/lapic.h
index 717fc9a..1d43b5f 100644
--- a/src/include/cpu/x86/lapic.h
+++ b/src/include/cpu/x86/lapic.h
@@ -10,6 +10,9 @@

static inline bool is_x2apic_mode(void)
 {
+	if (!CONFIG(X2APIC_SUPPORT))
+		return false;
+
    msr_t msr;
    msr = rdmsr(LAPIC_BASE_MSR);
    return ((msr.lo & LAPIC_BASE_X2APIC_ENABLED) == LAPIC_BASE_X2APIC_ENABLED);