linux-kernel - [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is

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Message-Id: <20251118080656.2012805-3-maobibo@loongson.cn>
Date: Tue, 18 Nov 2025 16:06:55 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Paolo Bonzini <pbonzini@...hat.com>,
	Huacai Chen <chenhuacai@...nel.org>,
	WANG Xuerui <kernel@...0n.name>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Will Deacon <will@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Waiman Long <longman@...hat.com>,
	Juergen Gross <jgross@...e.com>,
	Ajay Kaher <ajay.kaher@...adcom.com>,
	Alexey Makhalov <alexey.makhalov@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>
Cc: kvm@...r.kernel.org,
	loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux.dev,
	x86@...nel.org
Subject: [PATCH 2/3] LoongArch: Add paravirt support with vcpu_is_preempted()

Function vcpu_is_preempted() is used to check whether vCPU is preempted
or not. Here add implementation with vcpu_is_preempted() when option
CONFIG_PARAVIRT is enabled.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 arch/loongarch/include/asm/smp.h      |  1 +
 arch/loongarch/include/asm/spinlock.h |  5 +++++
 arch/loongarch/kernel/paravirt.c      | 16 ++++++++++++++++
 arch/loongarch/kernel/smp.c           |  6 ++++++
 4 files changed, 28 insertions(+)

diff --git a/arch/loongarch/include/asm/smp.h b/arch/loongarch/include/asm/smp.h
index 3a47f52959a8..5b37f7bf2060 100644
--- a/arch/loongarch/include/asm/smp.h
+++ b/arch/loongarch/include/asm/smp.h
@@ -18,6 +18,7 @@ struct smp_ops {
 	void (*init_ipi)(void);
 	void (*send_ipi_single)(int cpu, unsigned int action);
 	void (*send_ipi_mask)(const struct cpumask *mask, unsigned int action);
+	bool (*vcpu_is_preempted)(int cpu);
 };
 extern struct smp_ops mp_ops;
 
diff --git a/arch/loongarch/include/asm/spinlock.h b/arch/loongarch/include/asm/spinlock.h
index 7cb3476999be..c001cef893aa 100644
--- a/arch/loongarch/include/asm/spinlock.h
+++ b/arch/loongarch/include/asm/spinlock.h
@@ -5,6 +5,11 @@
 #ifndef _ASM_SPINLOCK_H
 #define _ASM_SPINLOCK_H
 
+#ifdef CONFIG_PARAVIRT
+#define vcpu_is_preempted	vcpu_is_preempted
+bool vcpu_is_preempted(int cpu);
+#endif
+
 #include <asm/processor.h>
 #include <asm/qspinlock.h>
 #include <asm/qrwlock.h>
diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
index b1b51f920b23..b99404b6b13f 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -52,6 +52,13 @@ static u64 paravt_steal_clock(int cpu)
 #ifdef CONFIG_SMP
 static struct smp_ops native_ops;
 
+static bool pv_vcpu_is_preempted(int cpu)
+{
+	struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+
+	return !!(src->preempted & KVM_VCPU_PREEMPTED);
+}
+
 static void pv_send_ipi_single(int cpu, unsigned int action)
 {
 	int min, old;
@@ -308,6 +315,9 @@ int __init pv_time_init(void)
 		pr_err("Failed to install cpu hotplug callbacks\n");
 		return r;
 	}
+
+	if (kvm_para_has_feature(KVM_FEATURE_PREEMPT_HINT))
+		mp_ops.vcpu_is_preempted = pv_vcpu_is_preempted;
 #endif
 
 	static_call_update(pv_steal_clock, paravt_steal_clock);
@@ -332,3 +342,9 @@ int __init pv_spinlock_init(void)
 
 	return 0;
 }
+
+bool notrace vcpu_is_preempted(int cpu)
+{
+	return mp_ops.vcpu_is_preempted(cpu);
+}
+EXPORT_SYMBOL(vcpu_is_preempted);
diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
index 46036d98da75..f04192fedf8d 100644
--- a/arch/loongarch/kernel/smp.c
+++ b/arch/loongarch/kernel/smp.c
@@ -307,10 +307,16 @@ static void loongson_init_ipi(void)
 		panic("IPI IRQ request failed\n");
 }
 
+static bool loongson_vcpu_is_preempted(int cpu)
+{
+	return false;
+}
+
 struct smp_ops mp_ops = {
 	.init_ipi		= loongson_init_ipi,
 	.send_ipi_single	= loongson_send_ipi_single,
 	.send_ipi_mask		= loongson_send_ipi_mask,
+	.vcpu_is_preempted	= loongson_vcpu_is_preempted,
 };
 
 static void __init fdt_smp_setup(void)
-- 
2.39.3