There are cases where a guest tries to switch spinlocks to bare metal behavior (e.g. by setting "xen_nopvspin" on XEN platform and "hv_nopvspin" on HYPER_V).
That feature is missed on KVM, add a new parameter "nopvspin" to disable PV spinlocks for KVM guest. This new parameter is also used to replace "xen_nopvspin" and "hv_nopvspin". The global variable pvspin isn't defined as __initdata as it's used at runtime by XEN guest. Signed-off-by: Zhenzhong Duan <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Radim Krcmar <[email protected]> Cc: Sean Christopherson <[email protected]> Cc: Vitaly Kuznetsov <[email protected]> Cc: Wanpeng Li <[email protected]> Cc: Jim Mattson <[email protected]> Cc: Joerg Roedel <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Will Deacon <[email protected]> --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ arch/x86/include/asm/qspinlock.h | 1 + arch/x86/kernel/kvm.c | 7 +++++++ kernel/locking/qspinlock.c | 7 +++++++ 4 files changed, 19 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index c7ac2f3..4b956d8 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5330,6 +5330,10 @@ as generic guest with no PV drivers. Currently support XEN HVM, KVM, HYPER_V and VMWARE guest. + nopvspin [X86,KVM] Disables the qspinlock slow path + using PV optimizations which allow the hypervisor to + 'idle' the guest on lock contention. + xirc2ps_cs= [NET,PCMCIA] Format: <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h index 444d6fd..34a4484 100644 --- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -32,6 +32,7 @@ static __always_inline u32 queued_fetch_set_pending_acquire(struct qspinlock *lo extern void __pv_init_lock_hash(void); extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val); extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock); +extern bool pvspin; #define queued_spin_unlock queued_spin_unlock /** diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index e820568..a4f108d 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -842,6 +842,13 @@ void __init kvm_spinlock_init(void) if (num_possible_cpus() == 1) return; + if (!pvspin) { + pr_info("PV spinlocks disabled\n"); + static_branch_disable(&virt_spin_lock_key); + return; + } + pr_info("PV spinlocks enabled\n"); + __pv_init_lock_hash(); pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath; pv_ops.lock.queued_spin_unlock = diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 2473f10..945b510 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -580,4 +580,11 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) #include "qspinlock_paravirt.h" #include "qspinlock.c" +bool pvspin = true; +static __init int parse_nopvspin(char *arg) +{ + pvspin = false; + return 0; +} +early_param("nopvspin", parse_nopvspin); #endif -- 1.8.3.1
