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Re: [PATCH] x86/PoD: defer nested P2M flushes


  • To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 19 Oct 2021 10:19:57 +0200
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  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>
  • Delivery-date: Tue, 19 Oct 2021 08:20:05 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 19.10.2021 10:17, Jan Beulich wrote:
> On 19.10.2021 10:09, Roger Pau Monné wrote:
>> On Mon, Oct 11, 2021 at 10:17:08AM +0200, Jan Beulich wrote:
>>> @@ -1229,8 +1242,9 @@ p2m_pod_demand_populate(struct p2m_domai
>>>          __trace_var(TRC_MEM_POD_POPULATE, 0, sizeof(t), &t);
>>>      }
>>>  
>>> -    pod_unlock(p2m);
>>> +    pod_unlock_and_flush(p2m);
>>>      return true;
>>> +
>>>  out_of_memory:
>>>      pod_unlock(p2m);
>>
>> Don't you need to set defer_nested_flush = false in the out_of_memory
>> label? (as you don't call pod_unlock_and_flush that would do it)
> 
> Yes of course - thanks for spotting. I had pod_unlock_and_flush() here
> too initially, and when switching back I forgot to convert rather than
> just delete that.

Oh, wait, that was on purpose: There's no point clearing the flag
when the next thing we do is invoke domain_crash(). If it wasn't
that way, I don't think I could avoid using pod_unlock_and_flush()
here as well.

Jan




 


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