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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id d78sm16644579wmd.47.2019.09.30.08.41.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Sep 2019 08:41:42 -0700 (PDT) From: Vitaly Kuznetsov To: Zhenzhong Duan , linux-kernel@vger.kernel.org Cc: Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Paolo Bonzini , Radim Krcmar , Sean Christopherson , Wanpeng Li , Jim Mattson , Joerg Roedel , Peter Zijlstra , Will Deacon Subject: Re: [PATCH 1/3] KVM: X86: Add "nopvspin" parameter to disable PV spinlocks In-Reply-To: <1569759666-26904-2-git-send-email-zhenzhong.duan@oracle.com> References: <1569759666-26904-1-git-send-email-zhenzhong.duan@oracle.com> <1569759666-26904-2-git-send-email-zhenzhong.duan@oracle.com> Date: Mon, 30 Sep 2019 17:41:41 +0200 Message-ID: <87pnjh3i6i.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Zhenzhong Duan writes: > 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. Any reason to not do it right now? We will probably need to have compat code to support xen_nopvspin/hv_nopvspin too but emit a 'is deprecated' warning. > > 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. Please do it in a separate patch. > > Signed-off-by: Zhenzhong Duan > Cc: Jonathan Corbet > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: Borislav Petkov > Cc: "H. Peter Anvin" > Cc: Paolo Bonzini > Cc: Radim Krcmar > Cc: Sean Christopherson > Cc: Vitaly Kuznetsov > Cc: Wanpeng Li > Cc: Jim Mattson > Cc: Joerg Roedel > Cc: Peter Zijlstra > Cc: Will Deacon > --- > 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: > ,,,,,[,[,[,]]] > 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 > */ > > +#define pr_fmt(fmt) "KVM: " fmt > + > #include > #include > #include > @@ -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 -- Vitaly