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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
commit | ace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch) | |
tree | b2d64bc10158fdd5497876388cd68142ca374ed3 /arch/x86/hyperv/hv_spinlock.c | |
parent | Initial commit. (diff) | |
download | linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip |
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/x86/hyperv/hv_spinlock.c')
-rw-r--r-- | arch/x86/hyperv/hv_spinlock.c | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/arch/x86/hyperv/hv_spinlock.c b/arch/x86/hyperv/hv_spinlock.c new file mode 100644 index 0000000000..737d6f7a61 --- /dev/null +++ b/arch/x86/hyperv/hv_spinlock.c @@ -0,0 +1,92 @@ +// 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 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) { + unsigned long msr_val; + + rdmsrl(HV_X64_MSR_GUEST_IDLE, msr_val); + + (void)msr_val; + } + local_irq_restore(flags); +} + +/* + * Hyper-V does not support this so far. + */ +__visible 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_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); |