Re: [Qemu-devel] [PATCH 0/4] exec: address space translation cleanups

[Paolo Bonzini <pbonzini@redhat.com>]

On 17/05/2017 09:17, Maxime Coquelin wrote:
> 
> 
> On 05/17/2017 07:57 AM, Peter Xu wrote:
>> On Wed, May 17, 2017 at 12:23:42PM +0800, Peter Xu wrote:
>>> On Tue, May 16, 2017 at 06:51:03PM +0200, Maxime Coquelin wrote:
>>>> Hi Peter,
>>>>
>>>> On 05/16/2017 03:24 PM, Maxime Coquelin wrote:
>>>>>
>>>>>
>>>>> On 05/15/2017 10:50 AM, Peter Xu wrote:
>>>>>> The problem is that, address_space_get_iotlb_entry() shares a lot
>>>>>> with
>>>>>> address_space_translate(). This patch tries to abstract the
>>>>>> shared elements.
>>>>>>
>>>>>> Originally, this work is derived from discussion from VT-d
>>>>>> passthrough
>>>>>> series discussions [1]. But for sure we can just see this series as a
>>>>>> standalone cleanup. So I posted it separately here.
>>>>>>
>>>>>> Smoke tests are done with general VM boots, IOs, especially with
>>>>>> vhost
>>>>>> dmar configurations.
>>>>>>
>>>>>> I believe with current series I can throw away the old patch [1],
>>>>>> which may be good. But before that, please kindly review. Thanks.
>>>>>
>>>>> I faced the problem the old patch fixes when declaring and
>>>>> attaching an
>>>>> IOMMU device, but booting the kernel with intel_iommu=off.
>>>>>
>>>>> I tested again with patches 1 & 4 of your series, and I confirm it
>>>>> fixes
>>>>> the issue:
>>>>> Tested-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>>>>
>>>> I did some more testing with my "vhost-user IOMMU" setup, and the
>>>> series
>>>> actually breaks with IOMMU device attached, and intel_iommu=on.
>>>>
>>>> The main difference with the previous passing test is the guest RAM
>>>> size. In the working setup, it is 2G of 2M hugepages, vs. 4G of 2M
>>>> hugepages in the failing one. Note that I also reproduce with
>>>> vhost-kernel
>>>> backend.
>>>>
>>>> The error happens in the first vhost_device_iotlb_miss() call:
>>>> qemu-system-x86_64: Fail to lookup the translated address b5d7c000
>>>>
>>>> I don't have the root cause yet, I'll keep you updated.
>>>
>>> Maxime,
>>>
>>> Thanks a lot for help testing this series!
>>>
>>> I reproduced this problem, and this is not a problem obvious enough
>>> for me. Let me investigate as well.
>>>
>>> -- 
>>> Peter Xu
>>
>> Maxime,
>>
>> Could you help try adding this change upon current to see whether
>> problem solved?
> 
> Hi Peter,
> 
> Yes, problem is solved with below change.

Cool---Peter, please send the new patch 4 as toplevel message!

Thanks,

Paolo