[v4,2/3] LoongArch: KVM: Implement function kvm_para_has_feature

Commit Message

Bibo Mao July 30, 2024, 7:53 a.m. UTC

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 <[e-mail]>
---
 arch/loongarch/include/asm/kvm_para.h | 10 ++++++++++
 arch/loongarch/kernel/paravirt.c      | 28 +++++++++++++++------------
 2 files changed, 26 insertions(+), 12 deletions(-)

Patch

diff --git a/arch/loongarch/include/asm/kvm_para.h b/arch/loongarch/include/asm/kvm_para.h
index 9814d56b8d0e..327f331d5237 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..10683e25b6b3 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 (!feature)
+		feature = read_cpucfg(CPUCFG_KVM_FEATURE);
+	return feature;
+}
+
+int __init pv_ipi_init(void)
+{
 	if (!kvm_para_available())
 		return 0;
 
-	feature = read_cpucfg(CPUCFG_KVM_FEATURE);
-	if (!(feature & BIT(KVM_FEATURE_IPI)))
+	if (!kvm_para_has_feature(KVM_FEATURE_IPI))
 		return 0;
 
 #ifdef CONFIG_SMP
@@ -258,15 +265,12 @@  static struct notifier_block pv_reboot_nb = {
 
 int __init pv_time_init(void)
 {
-	int r, feature;
+	int r;
 
-	if (!cpu_has_hypervisor)
-		return 0;
 	if (!kvm_para_available())
 		return 0;
 
-	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;