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SubjectRe: [PATCH v1 2/2] x86/hyperv: make HvNotifyLongSpinWait hypercall
On 18-10-19 16:20:52, Juergen Gross wrote:
> On 19/10/2018 15:13, Yi Sun wrote:

[...]

> > diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
> > index 0130e48..9e88c7e 100644
> > --- a/kernel/locking/qspinlock_paravirt.h
> > +++ b/kernel/locking/qspinlock_paravirt.h
> > @@ -7,6 +7,8 @@
> > #include <linux/bootmem.h>
> > #include <linux/debug_locks.h>
> >
> > +#include <asm/mshyperv.h>
> > +
> > /*
> > * Implement paravirt qspinlocks; the general idea is to halt the vcpus instead
> > * of spinning them.
> > @@ -305,6 +307,10 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
> > wait_early = true;
> > break;
> > }
> > +#if defined(CONFIG_X86_64) && defined(CONFIG_PARAVIRT_SPINLOCKS) && IS_ENABLED(CONFIG_HYPERV)
> > + if (!hv_notify_long_spin_wait(SPIN_THRESHOLD - loop))
> > + break;
> > +#endif
>
> I don't like that. Why should a KVM or Xen guest call into a hyperv
> specific function?
>
> Can't you move this to existing hyperv specific paravirt hooks?
>
hv_notify_long_spin_wait() must be called in this loop but it seems
there is no appropriate existing paravirt hook here. So, can I add
one more hook in pv_lock_ops to do this notification?

>
> Juergen

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