diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 5 | ||||
| -rw-r--r-- | arch/x86/hyperv/Makefile | 4 | ||||
| -rw-r--r-- | arch/x86/hyperv/hv_spinlock.c | 88 | ||||
| -rw-r--r-- | arch/x86/include/asm/mshyperv.h | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/mshyperv.c | 14 |
5 files changed, 113 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9871e649ffef..4cdf6a673592 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1385,6 +1385,11 @@ hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. If specified, z/VM IUCV HVC accepts connections from listed z/VM user IDs only. + + hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations + which allow the hypervisor to 'idle' the + guest on lock contention. + keep_bootcon [KNL] Do not unregister boot console at start. This is only useful for debugging when something happens in the window diff --git a/arch/x86/hyperv/Makefile b/arch/x86/hyperv/Makefile index b21ee65c4101..1c11f9420a82 100644 --- a/arch/x86/hyperv/Makefile +++ b/arch/x86/hyperv/Makefile @@ -1,2 +1,6 @@ obj-y := hv_init.o mmu.o nested.o obj-$(CONFIG_X86_64) += hv_apic.o + +ifdef CONFIG_X86_64 +obj-$(CONFIG_PARAVIRT_SPINLOCKS) += hv_spinlock.o +endif diff --git a/arch/x86/hyperv/hv_spinlock.c b/arch/x86/hyperv/hv_spinlock.c new file mode 100644 index 000000000000..a861b0456b1a --- /dev/null +++ b/arch/x86/hyperv/hv_spinlock.c @@ -0,0 +1,88 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Hyper-V specific spinlock code. + * + * Copyright (C) 2018, Intel, Inc. + * + * Author : Yi Sun <yi.y.sun@intel.com> + */ + +#define pr_fmt(fmt) "Hyper-V: " fmt + +#include <linux/spinlock.h> + +#include <asm/mshyperv.h> +#include <asm/paravirt.h> +#include <asm/apic.h> + +static bool __initdata hv_pvspin = true; + +static void hv_qlock_kick(int cpu) +{ + apic->send_IPI(cpu, X86_PLATFORM_IPI_VECTOR); +} + +static void hv_qlock_wait(u8 *byte, u8 val) +{ + unsigned long msr_val; + unsigned long flags; + + if (in_nmi()) + return; + + /* + * Reading HV_X64_MSR_GUEST_IDLE MSR tells the hypervisor that the + * vCPU can be put into 'idle' state. This 'idle' state is + * terminated by an IPI, usually from hv_qlock_kick(), even if + * interrupts are disabled on the vCPU. + * + * To prevent a race against the unlock path it is required to + * disable interrupts before accessing the HV_X64_MSR_GUEST_IDLE + * MSR. Otherwise, if the IPI from hv_qlock_kick() arrives between + * the lock value check and the rdmsrl() then the vCPU might be put + * into 'idle' state by the hypervisor and kept in that state for + * an unspecified amount of time. + */ + local_irq_save(flags); + /* + * Only issue the rdmsrl() when the lock state has not changed. + */ + if (READ_ONCE(*byte) == val) + rdmsrl(HV_X64_MSR_GUEST_IDLE, msr_val); + local_irq_restore(flags); +} + +/* + * Hyper-V does not support this so far. + */ +bool hv_vcpu_is_preempted(int vcpu) +{ + return false; +} +PV_CALLEE_SAVE_REGS_THUNK(hv_vcpu_is_preempted); + +void __init hv_init_spinlocks(void) +{ + if (!hv_pvspin || !apic || + !(ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) || + !(ms_hyperv.features & HV_X64_MSR_GUEST_IDLE_AVAILABLE)) { + pr_info("PV spinlocks disabled\n"); + 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 = PV_CALLEE_SAVE(__pv_queued_spin_unlock); + pv_ops.lock.wait = hv_qlock_wait; + pv_ops.lock.kick = hv_qlock_kick; + pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(hv_vcpu_is_preempted); +} + +static __init int hv_parse_nopvspin(char *arg) +{ + hv_pvspin = false; + return 0; +} +early_param("hv_nopvspin", hv_parse_nopvspin); diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h index f37704497d8f..0d6271cce198 100644 --- a/arch/x86/include/asm/mshyperv.h +++ b/arch/x86/include/asm/mshyperv.h @@ -351,6 +351,8 @@ int hyperv_flush_guest_mapping(u64 as); #ifdef CONFIG_X86_64 void hv_apic_init(void); +void __init hv_init_spinlocks(void); +bool hv_vcpu_is_preempted(int vcpu); #else static inline void hv_apic_init(void) {} #endif diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index ad12733f6058..1c72f3819eb1 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -199,6 +199,16 @@ static unsigned long hv_get_tsc_khz(void) return freq / 1000; } +#if defined(CONFIG_SMP) && IS_ENABLED(CONFIG_HYPERV) +static void __init hv_smp_prepare_boot_cpu(void) +{ + native_smp_prepare_boot_cpu(); +#if defined(CONFIG_X86_64) && defined(CONFIG_PARAVIRT_SPINLOCKS) + hv_init_spinlocks(); +#endif +} +#endif + static void __init ms_hyperv_init_platform(void) { int hv_host_info_eax; @@ -303,6 +313,10 @@ static void __init ms_hyperv_init_platform(void) if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE) alloc_intr_gate(HYPERV_STIMER0_VECTOR, hv_stimer0_callback_vector); + +# ifdef CONFIG_SMP + smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu; +# endif #endif } |