Re: [dpdk-dev] [External] RE: [PATCH v2] vhost: avoid iotlb mempool allocation while IOMMU disabled

["Xia, Chenbo" <chenbo.xia@intel.com>]

Hi,

> -----Original Message-----
> From: Wan Junjie <wanjunjie@bytedance.com>
> Sent: Thursday, May 13, 2021 6:52 PM
> To: Xia, Chenbo <chenbo.xia@intel.com>
> Cc: David Marchand <david.marchand@redhat.com>; Maxime Coquelin
> <maxime.coquelin@redhat.com>; dev@dpdk.org; Peng He
> <hepeng.0320@bytedance.com>; Zhihong Wang <wangzhihong.wzh@bytedance.com>;
> Thomas Monjalon <thomas@monjalon.net>
> Subject: Re: [External] RE: [dpdk-dev] [PATCH v2] vhost: avoid iotlb mempool
> allocation while IOMMU disabled
> 
> On Thu, May 13, 2021 at 6:24 PM Xia, Chenbo <chenbo.xia@intel.com> wrote:
> >
> > > -----Original Message-----
> > > From: David Marchand <david.marchand@redhat.com>
> > > Sent: Thursday, May 13, 2021 4:39 PM
> > > To: Xia, Chenbo <chenbo.xia@intel.com>; Maxime Coquelin
> > > <maxime.coquelin@redhat.com>
> > > Cc: Wan Junjie <wanjunjie@bytedance.com>; dev@dpdk.org; Peng He
> > > <hepeng.0320@bytedance.com>; Zhihong Wang <wangzhihong.wzh@bytedance.com>
> > > Subject: Re: [dpdk-dev] [PATCH v2] vhost: avoid iotlb mempool allocation
> while
> > > IOMMU disabled
> > >
> > > On Wed, Apr 7, 2021 at 9:10 AM Xia, Chenbo <chenbo.xia@intel.com> wrote:
> > > >
> > > > > -----Original Message-----
> > > > > From: Wan Junjie <wanjunjie@bytedance.com>
> > > > > Sent: Tuesday, February 2, 2021 4:15 PM
> > > > > To: Xia, Chenbo <chenbo.xia@intel.com>; Maxime Coquelin
> > > > > <maxime.coquelin@redhat.com>
> > > > > Cc: dev@dpdk.org; Wan Junjie <wanjunjie@bytedance.com>; Peng He
> > > > > <hepeng.0320@bytedance.com>; Zhihong Wang
> <wangzhihong.wzh@bytedance.com>
> > > > > Subject: [PATCH v2] vhost: avoid iotlb mempool allocation while IOMMU
> > > disabled
> > > > >
> > > > > If vhost device's IOMMU feature is disabled, iotlb mempool allocation
> > > > > is unnecessary.
> > > > >
> > > > > Reported-by: Peng He <hepeng.0320@bytedance.com>
> > > > > Signed-off-by: Wan Junjie <wanjunjie@bytedance.com>
> > > > > Reviewed-by: Zhihong Wang <wangzhihong.wzh@bytedance.com>
> > > > > ---
> > > > > 2.11.0
> > > >
> > > > Patch applied to next-virtio/main with conflict resolved, Thanks
> > >
> > > This patch triggered a regression reported by Red Hat QE.
> > > https://bugs.dpdk.org/show_bug.cgi?id=703
> > >
> 
> 
> > > Reverting the patch is enough to fix the regression.
> > >
> > > I'll let you guys decide on the next step for 21.05.
> > >
> > >
> > > --
> > > David Marchand
> >
> > I cannot reproduce this issue on my machine.
> >
> > @Wan Junjie Could you reproduce this? I prefer to revert the patch if things
> > are not very clear as it is only a minor optimization.
> >
> > Thanks,
> > Chenbo
> >
> >
> 
> Hi Chenbo,
> 
> I am not available for this now. Please revert it.
> Will dig it later.
> 
> Thanks,
> Junjie

I know the root cause, it is because when multi-queue is on, qemu only enable the
first queue pair and does not 'VHOST_USER_SET_VRING_NUM' for other queue pairs, which leads
to disabled queue pairs' iotlb_pool not init-ed. Then comes the iotlb message that operate
on all queue pairs iotlb pool.

A fix is coming.

Thanks,
Chenbo