From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Disables the qspinlock slow path using PV optimizations which
allow the hypervisor to 'idle' the guest on lock contention.
Reviewed-by: Leonardo Bras <leobras@xxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 2 +-
arch/riscv/kernel/qspinlock_paravirt.c | 13 +++++++++++++
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index b7794c96d91e..4aff81d741e2 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3927,7 +3927,7 @@
as generic guest with no PV drivers. Currently support
XEN HVM, KVM, HYPER_V and VMWARE guest.
- nopvspin [X86,XEN,KVM]
+ nopvspin [X86,XEN,KVM,RISC-V]
Disables the qspinlock slow path using PV optimizations
which allow the hypervisor to 'idle' the guest on lock
contention.
diff --git a/arch/riscv/kernel/qspinlock_paravirt.c b/arch/riscv/kernel/qspinlock_paravirt.c
index 7d1b99412222..4b04c93c4b9b 100644
--- a/arch/riscv/kernel/qspinlock_paravirt.c
+++ b/arch/riscv/kernel/qspinlock_paravirt.c
@@ -43,8 +43,21 @@ EXPORT_STATIC_CALL(pv_queued_spin_lock_slowpath);
DEFINE_STATIC_CALL(pv_queued_spin_unlock, native_queued_spin_unlock);
EXPORT_STATIC_CALL(pv_queued_spin_unlock);
+static bool nopvspin __initdata;
+static __init int parse_nopvspin(char *arg)
+{
+ nopvspin = true;
+ return 0;
+}
+early_param("nopvspin", parse_nopvspin);
+
void __init pv_qspinlock_init(void)
{
+ if (nopvspin) {
+ pr_info("PV qspinlocks disabled\n");
+ return;
+ }
+
if (num_possible_cpus() == 1)
return;
--
2.40.1
