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SubjectRe: [PATCH 3/4] paravirt: add virt_spin_lock pvops function
On Tue, Sep 05, 2017 at 03:24:43PM +0200, Juergen Gross wrote:
> diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
> index 48a706f641f2..fbd98896385c 100644
> --- a/arch/x86/include/asm/qspinlock.h
> +++ b/arch/x86/include/asm/qspinlock.h
> @@ -17,6 +17,25 @@ static inline void native_queued_spin_unlock(struct qspinlock *lock)
> smp_store_release((u8 *)lock, 0);
> }
>


Should this not have:

#ifdef CONFIG_PARAVIRT

?

> +static inline bool native_virt_spin_lock(struct qspinlock *lock)
> +{
> + if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
> + return false;
> +
> + /*
> + * On hypervisors without PARAVIRT_SPINLOCKS support we fall
> + * back to a Test-and-Set spinlock, because fair locks have
> + * horrible lock 'holder' preemption issues.
> + */
> +
> + do {
> + while (atomic_read(&lock->val) != 0)
> + cpu_relax();
> + } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0);
> +
> + return true;
> +}

#endif

> +
> #ifdef CONFIG_PARAVIRT_SPINLOCKS
> extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
> extern void __pv_init_lock_hash(void);


> #ifdef CONFIG_PARAVIRT
> #define virt_spin_lock virt_spin_lock
> +#ifdef CONFIG_PARAVIRT_SPINLOCKS
> static inline bool virt_spin_lock(struct qspinlock *lock)
> {
> + return pv_virt_spin_lock(lock);
> +}
> +#else
> +static inline bool virt_spin_lock(struct qspinlock *lock)
> +{
> + return native_virt_spin_lock(lock);
> }
> +#endif /* CONFIG_PARAVIRT_SPINLOCKS */
> #endif /* CONFIG_PARAVIRT */

Because I think the above only ever uses native_virt_spin_lock() when
PARAVIRT.

> @@ -1381,6 +1382,7 @@ void __init native_smp_prepare_boot_cpu(void)
> /* already set me in cpu_online_mask in boot_cpu_init() */
> cpumask_set_cpu(me, cpu_callout_mask);
> cpu_set_state_online(me);
> + native_pv_lock_init();
> }

Aah, this is where that goes.. OK that works too.

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