FROMGIT: LoongArch: KVM: Rework kvm_send_pv_ipi()

The function in fact traverses a "bitmap" stored in GPR regs A1 and A2,
but does it in a non-obvious way by creating a single-word bitmap twice.

This patch switches the function to create a single 2-word bitmap, and
also employs for_each_set_bit() macro, as it helps to drop most of the
housekeeping code.

While there, convert the function to return void to not confuse readers
with unchecked result.

Reviewed-by: Bibo Mao <[email protected]>
Signed-off-by: Yury Norov (NVIDIA) <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>

(cherry picked from commit 640f842
 https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson.git loongarch-next)
Signed-off-by: Kexy Biscuit <[email protected]>

Author: YuryNorov

arch/loongarch/kvm/exit.c

@@ -821,32 +821,25 @@ static int kvm_handle_lbt_disabled(struct kvm_vcpu *vcpu, int ecode)
 	return RESUME_GUEST;
 }
 
-static int kvm_send_pv_ipi(struct kvm_vcpu *vcpu)
+static void kvm_send_pv_ipi(struct kvm_vcpu *vcpu)
 {
-	unsigned int min, cpu, i;
-	unsigned long ipi_bitmap;
+	unsigned int min, cpu;
 	struct kvm_vcpu *dest;
+	DECLARE_BITMAP(ipi_bitmap, BITS_PER_LONG * 2) = {
+		kvm_read_reg(vcpu, LOONGARCH_GPR_A1),
+		kvm_read_reg(vcpu, LOONGARCH_GPR_A2)
+	};
 
 	min = kvm_read_reg(vcpu, LOONGARCH_GPR_A3);
-	for (i = 0; i < 2; i++, min += BITS_PER_LONG) {
-		ipi_bitmap = kvm_read_reg(vcpu, LOONGARCH_GPR_A1 + i);
-		if (!ipi_bitmap)
+	for_each_set_bit(cpu, ipi_bitmap, BITS_PER_LONG * 2) {
+		dest = kvm_get_vcpu_by_cpuid(vcpu->kvm, cpu + min);
+		if (!dest)
 			continue;
 
-		cpu = find_first_bit((void *)&ipi_bitmap, BITS_PER_LONG);
-		while (cpu < BITS_PER_LONG) {
-			dest = kvm_get_vcpu_by_cpuid(vcpu->kvm, cpu + min);
-			cpu = find_next_bit((void *)&ipi_bitmap, BITS_PER_LONG, cpu + 1);
-			if (!dest)
-				continue;
-
-			/* Send SWI0 to dest vcpu to emulate IPI interrupt */
-			kvm_queue_irq(dest, INT_SWI0);
-			kvm_vcpu_kick(dest);
-		}
+		/* Send SWI0 to dest vcpu to emulate IPI interrupt */
+		kvm_queue_irq(dest, INT_SWI0);
+		kvm_vcpu_kick(dest);
 	}
-
-	return 0;
 }
 
 /*