linux-kernel - [PATCH v6 2/3] LoongArch: KVM: Implement function kvm_para_has

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Message-Id: <20240812030210.500240-3-maobibo@loongson.cn>
Date: Mon, 12 Aug 2024 11:02:09 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Tianrui Zhao <zhaotianrui@...ngson.cn>,
	Huacai Chen <chenhuacai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc: WANG Xuerui <kernel@...0n.name>,
	kvm@...r.kernel.org,
	loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux.dev,
	x86@...nel.org,
	Song Gao <gaosong@...ngson.cn>
Subject: [PATCH v6 2/3] LoongArch: KVM: Implement function kvm_para_has_feature

Function kvm_para_has_feature() is to detect supported paravirt features,
it can be used by device driver to detect and enable paravirt features,
such as extioi irqchip driver can detect KVM_FEATURE_VIRT_EXTIOI and do
some optimization.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 arch/loongarch/include/asm/kvm_para.h | 10 +++++++++
 arch/loongarch/kernel/paravirt.c      | 31 ++++++++++++++-------------
 2 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/arch/loongarch/include/asm/kvm_para.h b/arch/loongarch/include/asm/kvm_para.h
index 39d7483ab8fd..2174fb53c2e7 100644
--- a/arch/loongarch/include/asm/kvm_para.h
+++ b/arch/loongarch/include/asm/kvm_para.h
@@ -155,10 +155,20 @@ static __always_inline long kvm_hypercall5(u64 fid,
 	return ret;
 }
 
+#ifdef CONFIG_PARAVIRT
+bool kvm_para_available(void);
+unsigned int kvm_arch_para_features(void);
+#else
+static inline bool kvm_para_available(void)
+{
+	return false;
+}
+
 static inline unsigned int kvm_arch_para_features(void)
 {
 	return 0;
 }
+#endif
 
 static inline unsigned int kvm_arch_para_hints(void)
 {
diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
index cc6bf096cb88..dc3cebcb550a 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -151,11 +151,14 @@ static void pv_init_ipi(void)
 }
 #endif
 
-static bool kvm_para_available(void)
+bool kvm_para_available(void)
 {
 	int config;
 	static int hypervisor_type;
 
+	if (!cpu_has_hypervisor)
+		return false;
+
 	if (!hypervisor_type) {
 		config = read_cpucfg(CPUCFG_KVM_SIG);
 		if (!memcmp(&config, KVM_SIGNATURE, 4))
@@ -165,17 +168,21 @@ static bool kvm_para_available(void)
 	return hypervisor_type == HYPERVISOR_KVM;
 }
 
-int __init pv_ipi_init(void)
+unsigned int kvm_arch_para_features(void)
 {
-	int feature;
+	static int feature;
 
-	if (!cpu_has_hypervisor)
-		return 0;
 	if (!kvm_para_available())
 		return 0;
 
-	feature = read_cpucfg(CPUCFG_KVM_FEATURE);
-	if (!(feature & BIT(KVM_FEATURE_IPI)))
+	if (!feature)
+		feature = read_cpucfg(CPUCFG_KVM_FEATURE);
+	return feature;
+}
+
+int __init pv_ipi_init(void)
+{
+	if (!kvm_para_has_feature(KVM_FEATURE_IPI))
 		return 0;
 
 #ifdef CONFIG_SMP
@@ -258,15 +265,9 @@ static struct notifier_block pv_reboot_nb = {
 
 int __init pv_time_init(void)
 {
-	int r, feature;
-
-	if (!cpu_has_hypervisor)
-		return 0;
-	if (!kvm_para_available())
-		return 0;
+	int r;
 
-	feature = read_cpucfg(CPUCFG_KVM_FEATURE);
-	if (!(feature & BIT(KVM_FEATURE_STEAL_TIME)))
+	if (!kvm_para_has_feature(KVM_FEATURE_STEAL_TIME))
 		return 0;
 
 	has_steal_clock = 1;
-- 
2.39.3