linux-kernel - [PATCH v3 04/17] x86/apic: Initialize APIC ID for Secure AVIC

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Message-ID: <20250401113616.204203-5-Neeraj.Upadhyay@amd.com>
Date: Tue, 1 Apr 2025 17:06:03 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: <linux-kernel@...r.kernel.org>
CC: <bp@...en8.de>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<dave.hansen@...ux.intel.com>, <Thomas.Lendacky@....com>, <nikunj@....com>,
	<Santosh.Shukla@....com>, <Vasant.Hegde@....com>,
	<Suravee.Suthikulpanit@....com>, <David.Kaplan@....com>, <x86@...nel.org>,
	<hpa@...or.com>, <peterz@...radead.org>, <seanjc@...gle.com>,
	<pbonzini@...hat.com>, <kvm@...r.kernel.org>,
	<kirill.shutemov@...ux.intel.com>, <huibo.wang@....com>,
	<naveen.rao@....com>, <francescolavra.fl@...il.com>
Subject: [PATCH v3 04/17] x86/apic: Initialize APIC ID for Secure AVIC

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

Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
---
Changes since v2:
 - Drop duplicate APIC ID checks.

 arch/x86/kernel/apic/x2apic_savic.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/x86/kernel/apic/x2apic_savic.c b/arch/x86/kernel/apic/x2apic_savic.c
index f1dd74724769..21f7c055995e 100644
--- a/arch/x86/kernel/apic/x2apic_savic.c
+++ b/arch/x86/kernel/apic/x2apic_savic.c
@@ -185,12 +185,25 @@ static void x2apic_savic_send_ipi_mask_allbutself(const struct cpumask *mask, in
 	__send_ipi_mask(mask, vector, true);
 }
 
+static void init_apic_page(void)
+{
+	u32 apic_id;
+
+	/*
+	 * Before Secure AVIC is enabled, APIC msr reads are intercepted.
+	 * APIC_ID msr read returns the value from the Hypervisor.
+	 */
+	apic_id = native_apic_msr_read(APIC_ID);
+	set_reg(APIC_ID, apic_id);
+}
+
 static void x2apic_savic_setup(void)
 {
 	void *backing_page;
 	enum es_result ret;
 	unsigned long gpa;
 
+	init_apic_page();
 	backing_page = this_cpu_ptr(apic_page);
 	gpa = __pa(backing_page);
 
-- 
2.34.1