Re: [Xen-devel] [PATCH v4] x86/apicv: fix RTC periodic timer and apicv issue

["Xuquan (Quan Xu)" <xuquan8@xxxxxxxxxx>]

>-----Original Message-----
>From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>Sent: Tuesday, January 03, 2017 3:35 PM
>To: Xuquan (Quan Xu)
>Cc: Andrew Cooper; George Dunlap; yang.zhang.wz@xxxxxxxxx; Chao Gao;
>Jun Nakajima; Kevin Tian; Lan Tianyu; xen-devel@xxxxxxxxxxxxx
>Subject: RE: [PATCH v4] x86/apicv: fix RTC periodic timer and apicv issue
>
>>>> On 23.12.16 at 13:24, <xuquan8@xxxxxxxxxx> wrote:
>> On December 22, 2016 4:12 PM, Jan Beulich wrote:
>>>>>> On 21.12.16 at 06:44, <xuquan8@xxxxxxxxxx> wrote:
>>>> --- a/xen/arch/x86/hvm/vmx/intr.c
>>>> +++ b/xen/arch/x86/hvm/vmx/intr.c
>>>> @@ -315,9 +315,13 @@ void vmx_intr_assist(void)
>>>>          * Set eoi_exit_bitmap for periodic timer interrup to cause
>>>EOI-induced VM
>>>>          * exit, then pending periodic time interrups have the
>>>> chance
>>>to be injected
>>>>          * for compensation
>>>> +        * Set eoi_exit_bitmap for intack.vector when it's higher
>>>> + than
>>>pending
>>>> +        * periodic time interrupts. This way we can guarantee
>>>> + there's
>>>always a chance
>>>> +        * to post periodic time interrupts when periodic time
>>>interrupts becomes the
>>>> +        * highest one
>>>>          */
>>>>          if (pt_vector != -1)
>>>> -            vmx_set_eoi_exit_bitmap(v, pt_vector);
>>>> +            vmx_set_eoi_exit_bitmap(v, intack.vector);
>>>
>>>The comment does not clarify why max(pt_vector, intack.vector) is not
>>>needed. And I'd expect you to add ASSERT(intack.vector >= pt_vector)
>>>then, to prove this (and one might argue that this addition could be
>>>sufficient documentation, albeit perhaps a brief comment next to the
>>>assertion would help readers of this non-trivial piece of code).
>>>
>> Kevin or Jan..
>> ASSERT(...) is ok to me.. Could you help me give a brief comment?
>
>I don't see why you couldn't simply use what Kevin said in reply to my
>earlier question regarding the lack of max() here.
>

What about """ Set EOI exit bitmap for any vector which may block injection of 
pt_vector - give a chance to recognize pt_vector in future intack and then do 
pt interrupts post"""?

Quan

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