LoongArch: Revert qspinlock to test-and-set simple lock on VM

Similar with x86, when VM is detected, revert to a simple test-and-set
lock to avoid the horrors of queue preemption.

Tested on 3C5000 Dual-way machine with 32 cores and 2 numa nodes,
test case is kcbench on kernel mainline 6.10, the detailed command is
"kcbench --src /root/src/linux"

Performance on host machine
                      kernel compile time       performance impact
   Original           150.29 seconds
   With patch         150.19 seconds            almost no impact

Performance on virtual machine:
1. 1 VM with 32 vCPUs and 2 numa node, numa node pinned
                      kernel compile time       performance impact
   Original           170.87 seconds
   With patch         171.73 seconds            almost no impact

2. 2 VMs, each VM with 32 vCPUs and 2 numa node, numa node pinned
                      kernel compile time       performance impact
   Original           2362.04 seconds
   With patch         354.73  seconds            +565%

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

3 files changed, 16 insertions, 1 deletions

diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
index 9c9b75b76f62..32537e9b1708 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -13,6 +13,7 @@ static int has_steal_clock;
 struct static_key paravirt_steal_enabled;
 struct static_key paravirt_steal_rq_enabled;
 static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
+DEFINE_STATIC_KEY_FALSE(virt_spin_lock_key);
 
 static u64 native_steal_clock(int cpu)
 {
@@ -300,3 +301,13 @@ int __init pv_time_init(void)
 
 	return 0;
 }
+
+int __init pv_spinlock_init(void)
+{
+	if (!cpu_has_hypervisor)
+		return 0;
+
+	static_branch_enable(&virt_spin_lock_key);
+
+	return 0;
+}
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 0f0740f0be27..00e307203ddb 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -603,6 +603,8 @@ void __init setup_arch(char **cmdline_p)
 	arch_mem_init(cmdline_p);
 
 	resource_init();
+	jump_label_init(); /* Initialise the static keys for paravirtualization */
+
 #ifdef CONFIG_SMP
 	plat_smp_setup();
 	prefill_possible_map();
diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
index ca405ab86aae..482b3c7e3042 100644
--- a/arch/loongarch/kernel/smp.c
+++ b/arch/loongarch/kernel/smp.c
@@ -476,7 +476,7 @@ core_initcall(ipi_pm_init);
 #endif
 
 /* Preload SMP state for boot cpu */
-void smp_prepare_boot_cpu(void)
+void __init smp_prepare_boot_cpu(void)
 {
 	unsigned int cpu, node, rr_node;
 
@@ -509,6 +509,8 @@ void smp_prepare_boot_cpu(void)
 			rr_node = next_node_in(rr_node, node_online_map);
 		}
 	}
+
+	pv_spinlock_init();
 }
 
 /* called from main before smp_init() */