Re: [Xen-devel] [xen-unstable test] 106504: regressions - FAIL

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

On March 22, 2017 2:14 PM, Chao Gao wrote:
>On Wed, Mar 22, 2017 at 06:47:33AM -0600, Jan Beulich wrote:
>>> 3. We read RTE 3 times. 1st happens when we set vIRR. 2nd happens
>>> when
>>> pt_update_irq() returns. 3rd happens in pt_intr_post(). If guest
>>> changes the vector in RTE during the window, it will also incur
>>> losing or getting more periodic timer interrupt.
>>
>>Which raises the question whether latching the value read the first
>>time would address the issue you demonstrate with the test case.
>>Or alternatively deferring writes to take effect only once readers are
>>done with their perhaps multiple accesses?
>
>I think your solution is better.
>
>>
>>Can you get in touch with your chipset folks to find out whether
>>hardware has cases where multiple reads occur during the processing of
>>a single event?
>
>Yes, I will come back once I get how they handle similar processes.
>
>>

Chao,
Based on Jan's suggestion, a rcu lock may be helpful to you..
Specifically, you can refer to rcu_read_lock() in kvm code..

btw, I still can't get how this caused the assertion clearly.. could you 
describe it in short? :)



Quan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel