Messages in this thread Patch in this message | | | From | Zhenzhong Duan <> | Subject | [PATCH 1/3] KVM: X86: Add "nopvspin" parameter to disable PV spinlocks | Date | Sun, 29 Sep 2019 20:21:04 +0800 |
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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 intended to replace "xen_nopvspin" and "hv_nopvspin" in the future.
The global variable pvspin isn't defined as __initdata as it's used at runtime by XEN guest.
Refactor the print stuff with pr_* which is preferred.
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krcmar <rkrcmar@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Wanpeng Li <wanpengli@tencent.com> Cc: Jim Mattson <jmattson@google.com> Cc: Joerg Roedel <joro@8bytes.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ arch/x86/include/asm/qspinlock.h | 1 + arch/x86/kernel/kvm.c | 27 ++++++++++++++++--------- kernel/locking/qspinlock.c | 7 +++++++ 4 files changed, 30 insertions(+), 9 deletions(-)
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..7b8cf0d 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -7,6 +7,8 @@ * Authors: Anthony Liguori <aliguori@us.ibm.com> */ +#define pr_fmt(fmt) "KVM: " fmt + #include <linux/context_tracking.h> #include <linux/init.h> #include <linux/kernel.h> @@ -286,7 +288,7 @@ static void kvm_register_steal_time(void) return; wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED)); - pr_info("kvm-stealtime: cpu %d, msr %llx\n", + pr_info("stealtime: cpu %d, msr %llx\n", cpu, (unsigned long long) slow_virt_to_phys(st)); } @@ -321,7 +323,7 @@ static void kvm_guest_cpu_init(void) wrmsrl(MSR_KVM_ASYNC_PF_EN, pa); __this_cpu_write(apf_reason.enabled, 1); - printk(KERN_INFO"KVM setup async PF for cpu %d\n", + pr_info("setup async PF for cpu %d\n", smp_processor_id()); } @@ -347,7 +349,7 @@ static void kvm_pv_disable_apf(void) wrmsrl(MSR_KVM_ASYNC_PF_EN, 0); __this_cpu_write(apf_reason.enabled, 0); - printk(KERN_INFO"Unregister pv shared memory for cpu %d\n", + pr_info("Unregister pv shared memory for cpu %d\n", smp_processor_id()); } @@ -509,7 +511,7 @@ static void kvm_setup_pv_ipi(void) { apic->send_IPI_mask = kvm_send_ipi_mask; apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself; - pr_info("KVM setup pv IPIs\n"); + pr_info("setup pv IPIs\n"); } static void kvm_smp_send_call_func_ipi(const struct cpumask *mask) @@ -639,11 +641,11 @@ static void __init kvm_guest_init(void) !kvm_para_has_hint(KVM_HINTS_REALTIME) && kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) { smp_ops.send_call_func_ipi = kvm_smp_send_call_func_ipi; - pr_info("KVM setup pv sched yield\n"); + pr_info("setup pv sched yield\n"); } if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online", kvm_cpu_online, kvm_cpu_down_prepare) < 0) - pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n"); + pr_err("failed to install cpu hotplug callbacks\n"); #else sev_map_percpu_data(); kvm_guest_cpu_init(); @@ -746,7 +748,7 @@ static __init int kvm_setup_pv_tlb_flush(void) zalloc_cpumask_var_node(per_cpu_ptr(&__pv_tlb_mask, cpu), GFP_KERNEL, cpu_to_node(cpu)); } - pr_info("KVM setup pv remote TLB flush\n"); + pr_info("setup pv remote TLB flush\n"); } return 0; @@ -842,6 +844,13 @@ 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 = @@ -872,8 +881,8 @@ static void kvm_enable_host_haltpoll(void *i) void arch_haltpoll_enable(unsigned int cpu) { if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) { - pr_err_once("kvm: host does not support poll control\n"); - pr_err_once("kvm: host upgrade recommended\n"); + pr_err_once("host does not support poll control\n"); + pr_err_once("host upgrade recommended\n"); return; } 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
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