linux-kernel - [PATCH v2 2/3] x86/apic: Add helper function to get maximum physical APIC ID

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Date:   Thu, 2 Dec 2021 17:58:24 -0600
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
        <x86@...nel.org>
CC:     <pbonzini@...hat.com>, <joro@...tes.org>, <seanjc@...gle.com>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <peterz@...radead.org>, <hpa@...or.com>, <thomas.lendacky@....com>,
        <jon.grimm@....com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v2 2/3] x86/apic: Add helper function to get maximum physical APIC ID

Export the max_physical_apicid via a helper function since this information
is required by AMD SVM AVIC support.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/include/asm/apic.h | 1 +
 arch/x86/kernel/apic/apic.c | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 48067af94678..77d9cb2a7e28 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -435,6 +435,7 @@ static inline void apic_set_eoi_write(void (*eoi_write)(u32 reg, u32 v)) {}
 #endif /* CONFIG_X86_LOCAL_APIC */
 
 extern void apic_ack_irq(struct irq_data *data);
+extern u32 apic_get_max_phys_apicid(void);
 
 static inline void ack_APIC_irq(void)
 {
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index b70344bf6600..47653d8c05f2 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2361,6 +2361,12 @@ bool apic_id_is_primary_thread(unsigned int apicid)
 }
 #endif
 
+u32 apic_get_max_phys_apicid(void)
+{
+	return max_physical_apicid;
+}
+EXPORT_SYMBOL_GPL(apic_get_max_phys_apicid);
+
 /*
  * Should use this API to allocate logical CPU IDs to keep nr_logical_cpuids
  * and cpuid_to_apicid[] synchronized.
-- 
2.25.1