linux-kernel - [PATCH] kvm: x86: simplify kvm_vector_to

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Message-ID: <20250720015846.433956-1-yury.norov@gmail.com>
Date: Sat, 19 Jul 2025 21:58:45 -0400
From: Yury Norov <yury.norov@...il.com>
To: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	x86@...nel.org,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>
Subject: [PATCH] kvm: x86: simplify kvm_vector_to_index()

Use find_nth_bit() and make the function almost a one-liner.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 arch/x86/kvm/lapic.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 73418dc0ebb2..6c4ec016de6a 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1106,16 +1106,10 @@ EXPORT_SYMBOL_GPL(kvm_apic_match_dest);
 int kvm_vector_to_index(u32 vector, u32 dest_vcpus,
 		       const unsigned long *bitmap, u32 bitmap_size)
 {
-	u32 mod;
-	int i, idx = -1;
-
-	mod = vector % dest_vcpus;
-
-	for (i = 0; i <= mod; i++) {
-		idx = find_next_bit(bitmap, bitmap_size, idx + 1);
-		BUG_ON(idx == bitmap_size);
-	}
+	u32 mod = vector % dest_vcpus;
+	int idx = find_nth_bit(bitmap, bitmap_size, mod);
 
+	BUG_ON(idx >= bitmap_size);
 	return idx;
 }
 
-- 
2.43.0