linux-kernel - [PATCH v4 01/18] KVM: x86: Move find_highest

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Message-ID: <20250417091708.215826-2-Neeraj.Upadhyay@amd.com>
Date: Thu, 17 Apr 2025 14:46:51 +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 v4 01/18] KVM: x86: Move find_highest_vector() to a common header

In preparation for using find_highest_vector() in Secure AVIC
guest APIC driver, move (and rename) find_highest_vector() to
apic.h.

Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
---
Changes since v3:

 - New patch to move KVM updates to a separate patch.

 arch/x86/include/asm/apic.h | 23 +++++++++++++++++++++++
 arch/x86/kvm/lapic.c        | 23 +++--------------------
 2 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 1c136f54651c..c63c2fe8ad13 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -500,6 +500,29 @@ static inline bool is_vector_pending(unsigned int vector)
 	return lapic_vector_set_in_irr(vector) || pi_pending_this_cpu(vector);
 }
 
+#define MAX_APIC_VECTOR			256
+#define APIC_VECTORS_PER_REG		32
+
+static inline int apic_find_highest_vector(void *bitmap)
+{
+	unsigned int regno;
+	unsigned int vec;
+	u32 *reg;
+
+	/*
+	 * The registers in the bitmap are 32-bit wide and 16-byte
+	 * aligned. State of a vector is stored in a single bit.
+	 */
+	for (regno = MAX_APIC_VECTOR / APIC_VECTORS_PER_REG - 1; regno >= 0; regno--) {
+		vec = regno * APIC_VECTORS_PER_REG;
+		reg = bitmap + regno * 16;
+		if (*reg)
+			return __fls(*reg) + vec;
+	}
+
+	return -1;
+}
+
 /*
  * Warm reset vector position:
  */
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 28e3317124fd..775eb742d110 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -27,6 +27,7 @@
 #include <linux/export.h>
 #include <linux/math64.h>
 #include <linux/slab.h>
+#include <asm/apic.h>
 #include <asm/processor.h>
 #include <asm/mce.h>
 #include <asm/msr.h>
@@ -55,9 +56,6 @@
 /* 14 is the version for Xeon and Pentium 8.4.8*/
 #define APIC_VERSION			0x14UL
 #define LAPIC_MMIO_LENGTH		(1 << 12)
-/* followed define is not in apicdef.h */
-#define MAX_APIC_VECTOR			256
-#define APIC_VECTORS_PER_REG		32
 
 /*
  * Enable local APIC timer advancement (tscdeadline mode only) with adaptive
@@ -626,21 +624,6 @@ static const unsigned int apic_lvt_mask[KVM_APIC_MAX_NR_LVT_ENTRIES] = {
 	[LVT_CMCI] = LVT_MASK | APIC_MODE_MASK
 };
 
-static int find_highest_vector(void *bitmap)
-{
-	int vec;
-	u32 *reg;
-
-	for (vec = MAX_APIC_VECTOR - APIC_VECTORS_PER_REG;
-	     vec >= 0; vec -= APIC_VECTORS_PER_REG) {
-		reg = bitmap + REG_POS(vec);
-		if (*reg)
-			return __fls(*reg) + vec;
-	}
-
-	return -1;
-}
-
 static u8 count_vectors(void *bitmap)
 {
 	int vec;
@@ -704,7 +687,7 @@ EXPORT_SYMBOL_GPL(kvm_apic_update_irr);
 
 static inline int apic_search_irr(struct kvm_lapic *apic)
 {
-	return find_highest_vector(apic->regs + APIC_IRR);
+	return apic_find_highest_vector(apic->regs + APIC_IRR);
 }
 
 static inline int apic_find_highest_irr(struct kvm_lapic *apic)
@@ -779,7 +762,7 @@ static inline int apic_find_highest_isr(struct kvm_lapic *apic)
 	if (likely(apic->highest_isr_cache != -1))
 		return apic->highest_isr_cache;
 
-	result = find_highest_vector(apic->regs + APIC_ISR);
+	result = apic_find_highest_vector(apic->regs + APIC_ISR);
 	ASSERT(result == -1 || result >= 16);
 
 	return result;
-- 
2.34.1