linux-kernel - [PATCH 1/2] LoongArch: KVM: rework kvm_send_pv

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250716165929.22386-2-yury.norov@gmail.com>
Date: Wed, 16 Jul 2025 12:59:26 -0400
From: Yury Norov <yury.norov@...il.com>
To: Tianrui Zhao <zhaotianrui@...ngson.cn>,
	Bibo Mao <maobibo@...ngson.cn>,
	Huacai Chen <chenhuacai@...nel.org>,
	WANG Xuerui <kernel@...0n.name>,
	kvm@...r.kernel.org,
	loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>
Subject: [PATCH 1/2] LoongArch: KVM: rework kvm_send_pv_ipi()

From: "Yury Norov (NVIDIA)" <yury.norov@...il.com>

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
housekeeping code.

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

Signed-off-by: Yury Norov (NVIDIA) <yury.norov@...il.com>
---
 arch/loongarch/kvm/exit.c | 31 ++++++++++++-------------------
 1 file changed, 12 insertions(+), 19 deletions(-)

diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
index fa52251b3bf1..359afa909cee 100644
--- a/arch/loongarch/kvm/exit.c
+++ b/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;
+	DECLARE_BITMAP(ipi_bitmap, BITS_PER_LONG * 2) = {
+		kvm_read_reg(vcpu, LOONGARCH_GPR_A1),
+		kvm_read_reg(vcpu, LOONGARCH_GPR_A2)
+	};
+	unsigned int min, cpu;
 	struct kvm_vcpu *dest;
 
 	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;
 }
 
 /*
-- 
2.43.0