On Mon, Sep 14, 2015 at 5:20 PM, Ian Campbell <ian.campb...@citrix.com> wrote:
> On Mon, 2015-09-14 at 14:40 +0200, Christoffer Dall wrote: > > On Fri, Jul 31, 2015 at 03:17:56PM +0200, Christoffer Dall wrote: > > > On Fri, Jul 31, 2015 at 12:28 PM, David Vrabel < > david.vra...@citrix.com > > > > > > > wrote: > > > > > > > On 31/07/15 11:24, Stefano Stabellini wrote: > > > > > This is a Linux Dom0 crash on x86 (Dell PowerEdge R320, Xeon E5 > > > > > -2450), > > > > > CC'ing relevant people. As you can see from the links below the > > > > > crash > > > > > is: > > > > > > > > > > [ 253.619326] Call Trace: > > > > > [ 253.619330] <IRQ> > > > > > [ 253.619332] [<ffffffff815d7c25>] ? skb_copy_ubufs+0xa5/0x230 > > > > > [ 253.619347] [<ffffffff815e8525>] > > > > > __netif_receive_skb_core+0x6f5/0x940 > > > > > [ 253.619353] [<ffffffff815e8788>] __netif_receive_skb+0x18/0x60 > > > > > [ 253.619360] [<ffffffff815e87f8>] > > > > > netif_receive_skb_internal+0x28/0x90 > > > > > [ 253.619366] [<ffffffff815e91f5>] napi_gro_frags+0x125/0x1a0 > > > > > [ 253.619378] [<ffffffffa01b1173>] > > > > > mlx4_en_process_rx_cq+0x753/0xb50 > > > > [mlx4_en] > > > > > [ 253.619387] [<ffffffffa01b1657>] mlx4_en_poll_rx_cq+0x97/0x160 > > > > [mlx4_en] > > > > > > > > What makes you think this is Xen specific? I suggest raising this > > > > the > > > > the mlx4 maintainers. > > > > > > > > > > > Linux native and KVM guests (same hw, same kernel version+config) run > > > just > > > fine under the same workload. > > > > > Ping? > > > > From the fact that bare-metal and KVM works fine with this hardware I > > still think it's reasonable to assume that it's a Xen issue and not a > > mlx4 issue. > > > > Is this completely flawed? > > My (somewhat educated) guess is that this is to do with the difference > between (pseudo-)physical addresses and machine (AKA real-physical) > addresses when running under Xen. > > The way this often shows up is in drivers which do not make correct use of > the kernels DMA APIs but which happen to work on native x86 because > physical==bus address on x86. > > Sometimes booting natively with 'iommu=soft swiotlb=force' can expose these > sorts of issues. > I'll give this a try. > > You are running 64-bit so I don't think the recent "config: Enable > NEED_DMA_MAP_STATE by default when SWIOTLB is selected" is likely to be > relevant (it's already unconditionally on for 64-bit). > > The trace appears to be on rx from a physical nic, there shouldn't be any > magic Xen stuff (granted pages etc) getting themselves into that path at > all. If it were tx then maybe it might be an issue with foreign pages. In > any case I think you are able to repro with just dom0, i.e. never having > started a domU, is that right? > As far as I remember and as far as I can interpret my own e-mail, yes. Thanks for the feedback, I'll try the suggested approaches and also try using v4.3-rc1 and take it up with the mlx4 maintainers if I still see the issue. -Christoffer
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