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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. The new 'nopvspin' parameter will also replace Xen and Hyper-V specific parameters in future patches. Define variable nopvsin as global because it will be used in future patches as above. Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.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> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
113 lines
3.1 KiB
C
113 lines
3.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_QSPINLOCK_H
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#define _ASM_X86_QSPINLOCK_H
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#include <linux/jump_label.h>
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#include <asm/cpufeature.h>
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#include <asm-generic/qspinlock_types.h>
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#include <asm/paravirt.h>
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#include <asm/rmwcc.h>
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#define _Q_PENDING_LOOPS (1 << 9)
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#define queued_fetch_set_pending_acquire queued_fetch_set_pending_acquire
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static __always_inline u32 queued_fetch_set_pending_acquire(struct qspinlock *lock)
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{
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u32 val;
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/*
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* We can't use GEN_BINARY_RMWcc() inside an if() stmt because asm goto
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* and CONFIG_PROFILE_ALL_BRANCHES=y results in a label inside a
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* statement expression, which GCC doesn't like.
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*/
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val = GEN_BINARY_RMWcc(LOCK_PREFIX "btsl", lock->val.counter, c,
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"I", _Q_PENDING_OFFSET) * _Q_PENDING_VAL;
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val |= atomic_read(&lock->val) & ~_Q_PENDING_MASK;
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return val;
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}
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
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extern void __pv_init_lock_hash(void);
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extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
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extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
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extern bool nopvspin;
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#define queued_spin_unlock queued_spin_unlock
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/**
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* queued_spin_unlock - release a queued spinlock
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* @lock : Pointer to queued spinlock structure
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*
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* A smp_store_release() on the least-significant byte.
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*/
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static inline void native_queued_spin_unlock(struct qspinlock *lock)
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{
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smp_store_release(&lock->locked, 0);
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}
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static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
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{
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pv_queued_spin_lock_slowpath(lock, val);
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}
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static inline void queued_spin_unlock(struct qspinlock *lock)
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{
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pv_queued_spin_unlock(lock);
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}
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#define vcpu_is_preempted vcpu_is_preempted
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static inline bool vcpu_is_preempted(long cpu)
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{
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return pv_vcpu_is_preempted(cpu);
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}
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#endif
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#ifdef CONFIG_PARAVIRT
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/*
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* virt_spin_lock_key - enables (by default) the virt_spin_lock() hijack.
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*
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* Native (and PV wanting native due to vCPU pinning) should disable this key.
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* It is done in this backwards fashion to only have a single direction change,
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* which removes ordering between native_pv_spin_init() and HV setup.
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*/
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DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key);
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void native_pv_lock_init(void) __init;
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/*
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* Shortcut for the queued_spin_lock_slowpath() function that allows
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* virt to hijack it.
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*
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* Returns:
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* true - lock has been negotiated, all done;
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* false - queued_spin_lock_slowpath() will do its thing.
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*/
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#define virt_spin_lock virt_spin_lock
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static inline bool virt_spin_lock(struct qspinlock *lock)
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{
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if (!static_branch_likely(&virt_spin_lock_key))
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return false;
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/*
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* On hypervisors without PARAVIRT_SPINLOCKS support we fall
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* back to a Test-and-Set spinlock, because fair locks have
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* horrible lock 'holder' preemption issues.
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*/
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do {
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while (atomic_read(&lock->val) != 0)
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cpu_relax();
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} while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0);
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return true;
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}
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#else
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static inline void native_pv_lock_init(void)
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{
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}
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#endif /* CONFIG_PARAVIRT */
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#include <asm-generic/qspinlock.h>
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#endif /* _ASM_X86_QSPINLOCK_H */
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