From 3a025de64bf89c84a79909069e3c24ad9e710d27 Mon Sep 17 00:00:00 2001 From: Yi Sun Date: Mon, 8 Oct 2018 16:29:34 +0800 Subject: x86/hyperv: Enable PV qspinlock for Hyper-V Implement the required wait and kick callbacks to support PV spinlocks in Hyper-V guests. [ tglx: Document the requirement for disabling interrupts in the wait() callback. Remove goto and unnecessary includes. Add prototype for hv_vcpu_is_preempted(). Adapted to pending paravirt changes. ] Signed-off-by: Yi Sun Signed-off-by: Thomas Gleixner Reviewed-by: Juergen Gross Cc: "K. Y. Srinivasan" Cc: Haiyang Zhang Cc: Stephen Hemminger Cc: Michael Kelley (EOSG) Cc: chao.p.peng@intel.com Cc: chao.gao@intel.com Cc: isaku.yamahata@intel.com Cc: tianyu.lan@microsoft.com Link: https://lkml.kernel.org/r/1538987374-51217-3-git-send-email-yi.y.sun@linux.intel.com --- arch/x86/hyperv/Makefile | 4 ++ arch/x86/hyperv/hv_spinlock.c | 88 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 92 insertions(+) create mode 100644 arch/x86/hyperv/hv_spinlock.c (limited to 'arch/x86/hyperv') 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 + */ + +#define pr_fmt(fmt) "Hyper-V: " fmt + +#include + +#include +#include +#include + +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); -- cgit v1.2.3