Re: [Xen-devel] [PATCH] VMX: wbinvd when vmentry under UC

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 29/11/13 14:15, Liu, Jinsong wrote:
> Jan Beulich wrote:
>>>>> "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> 11/28/13 8:17 AM >>>
>>> Liu, Jinsong wrote:
>>>> Yes. reprogram_timer here just delay timer a little slot, say,
>>>> 1~2ms. I think it's OK, i.e. at any point of wbinvd() operation at
>>>> hypervisor, or any irq disabled area, timer interrupt in fact also
>>>> has good chance to be delayed some time -- however at TIMER_SOFTIRQ,
>>>> all expired thing would be executed, and re-calculated and set next
>>>> time point via reprogram_timer -- that's OK.
>>> Comments/thoughts about this option?
>> Apart from continuing to be very uncertain that this won't have any
>> bad side effects, I'm also rather concerned that you deal with one
>> special case interrupt here, ignoring other potentially high rate ones
>> (like such coming from NICs).
>>
>> Jan
> Considering this, seems adding flag is the only work around way since high 
> freq interrupt would result in dead-like-loop. My concern of adding flag is 
> it's not easy to clean every possible path, especially future extension.
>
> Or, do not support vt-d w/o snoop.
>
> Thanks,
> Jinsong

Do you know how many systems have vt-d without snoop ?

~Andrew

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