From: Juergen Gross <jgross@suse.com>
To: Yi Sun <yi.y.sun@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de,
chao.p.peng@intel.com, chao.gao@intel.com,
isaku.yamahata@intel.com, michael.h.kelley@microsoft.com,
tianyu.lan@microsoft.com, "K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Peter Zijlstra <peterz@infradead.org>,
"mingo@redhat.com" <mingo@redhat.com>,
Will Deacon <will.deacon@arm.com>,
Waiman Long <longman@redhat.com>
Subject: Re: [PATCH v1 2/2] x86/hyperv: make HvNotifyLongSpinWait hypercall
Date: Mon, 22 Oct 2018 09:32:31 +0200 [thread overview]
Message-ID: <2e0d62cb-b706-a5b4-65f7-982a913fb32b@suse.com> (raw)
In-Reply-To: <20181022015342.GK11769@yi.y.sun>
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
next prev parent reply other threads:[~2018-10-22 7:32 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-19 13:13 [PATCH v1 0/2] Enable HvNotifyLongSpinWait for Hyper-V Yi Sun
2018-10-19 13:13 ` [PATCH v1 1/2] x86/hyperv: get spinlock retry number on Hyper-V Yi Sun
2018-10-19 13:13 ` [PATCH v1 2/2] x86/hyperv: make HvNotifyLongSpinWait hypercall Yi Sun
2018-10-19 14:20 ` Juergen Gross
2018-10-22 1:53 ` Yi Sun
2018-10-22 7:32 ` Juergen Gross [this message]
2018-10-22 16:31 ` Waiman Long
2018-10-22 17:15 ` Peter Zijlstra
2018-10-22 17:27 ` Waiman Long
2018-10-22 17:31 ` Peter Zijlstra
2018-10-22 18:01 ` Waiman Long
2018-10-23 2:57 ` Yi Sun
2018-10-23 8:51 ` Peter Zijlstra
2018-10-23 9:33 ` Yi Sun
2018-10-31 1:54 ` Yi Sun
2018-10-31 14:10 ` Peter Zijlstra
2018-10-31 15:07 ` Waiman Long
2018-10-31 17:15 ` Peter Zijlstra
2018-11-01 3:20 ` Yi Sun
2018-11-01 8:59 ` Peter Zijlstra
2018-11-01 12:59 ` Waiman Long
2018-11-05 6:54 ` Yi Sun
2018-10-24 16:53 ` Michael Kelley
2018-10-25 2:23 ` Yi Sun
2018-10-31 2:06 ` Yi Sun
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