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

[Peter Xu]

On Wed, May 17, 2017 at 09:26:25AM +0200, Paolo Bonzini wrote:
> 
> 
> 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 <address@hidden>
> >>>>
> >>>> 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!

Will do. Thanks!

-- 
Peter Xu