[PATCH] KVM: arm64: Convert kvm_mpidr_index() to bitmap_gather()

* [PATCH] KVM: arm64: Convert kvm_mpidr_index() to bitmap_gather()
@ 2024-05-02 15:42 Marc Zyngier
  2024-05-02 17:06 ` Oliver Upton
  2024-05-03 13:35 ` Marc Zyngier
  0 siblings, 2 replies; 3+ messages in thread
From: Marc Zyngier @ 2024-05-02 15:42 UTC (permalink / raw)
  To: kvmarm, kvm, linux-arm-kernel
  Cc: James Morse, Suzuki K Poulose, Oliver Upton, Zenghui Yu

Linux 6.9 has introduced new bitmap manipulation helpers, with
bitmap_gather() being of special interest, as it does exactly
what kvm_mpidr_index() is already doing.

Make the latter a wrapper around the former.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_host.h | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 23a117cb3e50..fe94e96dced8 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -221,20 +221,10 @@ struct kvm_mpidr_data {
 
 static inline u16 kvm_mpidr_index(struct kvm_mpidr_data *data, u64 mpidr)
 {
-	unsigned long mask = data->mpidr_mask;
-	u64 aff = mpidr & MPIDR_HWID_BITMASK;
-	int nbits, bit, bit_idx = 0;
-	u16 index = 0;
+	unsigned long index = 0, mask = data->mpidr_mask;
+	unsigned long aff = mpidr & MPIDR_HWID_BITMASK;
 
-	/*
-	 * If this looks like RISC-V's BEXT or x86's PEXT
-	 * instructions, it isn't by accident.
-	 */
-	nbits = fls(mask);
-	for_each_set_bit(bit, &mask, nbits) {
-		index |= (aff & BIT(bit)) >> (bit - bit_idx);
-		bit_idx++;
-	}
+	bitmap_gather(&index, &aff, &mask, fls(mask));
 
 	return index;
 }
-- 
2.39.2


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