[PATCH v10 04/18] x86/apic: Initialize APIC ID for Secure AVIC

[Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>]

Initialize the APIC ID in the Secure AVIC APIC backing page with
the APIC_ID MSR value read from the hypervisor. CPU topology evaluation
later during boot would catch and report any duplicate APIC ID for
two CPUs.

Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
---
Changes since v9:
 - Commit log update.

 arch/x86/kernel/apic/x2apic_savic.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/apic/x2apic_savic.c b/arch/x86/kernel/apic/x2apic_savic.c
index 5479605429c1..56c51ea4e5ab 100644
--- a/arch/x86/kernel/apic/x2apic_savic.c
+++ b/arch/x86/kernel/apic/x2apic_savic.c
@@ -150,6 +150,12 @@ static void savic_setup(void)
 	enum es_result res;
 	unsigned long gpa;
 
+	/*
+	 * Before Secure AVIC is enabled, APIC MSR reads are intercepted.
+	 * APIC_ID MSR read returns the value from the hypervisor.
+	 */
+	apic_set_reg(ap, APIC_ID, native_apic_msr_read(APIC_ID));
+
 	gpa = __pa(ap);
 
 	/*
-- 
2.34.1