Messages in this thread | | | Subject | Re: [PATCH v1 2/2] x86/hyperv: make HvNotifyLongSpinWait hypercall | From | Waiman Long <> | Date | Mon, 22 Oct 2018 12:31:45 -0400 |
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On 10/22/2018 03:32 AM, Juergen Gross wrote: > On 22/10/2018 03:53, Yi Sun wrote: >> 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? > vcpu_is_preempted() is already part of this loop. And this is a paravirt > hook. Can't you make use of that? This might require adding another > parameter to this hook, but I'd prefer that over another pv-spinlock > hook. > > Adding some more locking maintainers and Waiman to the Cc: list. > > > Juergen > I agree with Juergen on that. I would suggest rename the vcpu_is_preempted hook into a more generic vcpu_stop_spinning, perhaps, so different hypervisors can act on the information accordingly. Adding an extra parameter is fine.
Cheers, Longman
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