ARM64/KVM: Bad page state in process iperf

[Bhushan Bharat]

> -----Original Message-----
> From: Marc Zyngier [mailto:marc.zyngier at arm.com]
> Sent: Tuesday, December 15, 2015 4:49 PM
> To: Bhushan Bharat-R65777 <Bharat.Bhushan at freescale.com>;
> kvmarm at lists.cs.columbia.edu; kvm at vger.kernel.org; linux-arm-
> kernel at lists.infradead.org; linux-kernel at vger.kernel.org
> Subject: Re: ARM64/KVM: Bad page state in process iperf
> 
> On 15/12/15 10:57, Bhushan Bharat wrote:
> >
> >
> >> -----Original Message-----
> >> From: Marc Zyngier [mailto:marc.zyngier at arm.com]
> >> Sent: Tuesday, December 15, 2015 3:50 PM
> >> To: Bhushan Bharat-R65777 <Bharat.Bhushan at freescale.com>;
> >> kvmarm at lists.cs.columbia.edu; kvm at vger.kernel.org; linux-arm-
> >> kernel at lists.infradead.org; linux-kernel at vger.kernel.org
> >> Subject: Re: ARM64/KVM: Bad page state in process iperf
> >>
> >> On 15/12/15 09:53, Bhushan Bharat wrote:
> >>> Hi Mark,
> >>>
> >>>> -----Original Message-----
> >>>> From: Marc Zyngier [mailto:marc.zyngier at arm.com]
> >>>> Sent: Tuesday, December 15, 2015 3:05 PM
> >>>> To: Bhushan Bharat-R65777 <Bharat.Bhushan at freescale.com>;
> >>>> kvmarm at lists.cs.columbia.edu; kvm at vger.kernel.org; linux-arm-
> >>>> kernel at lists.infradead.org; linux-kernel at vger.kernel.org
> >>>> Subject: Re: ARM64/KVM: Bad page state in process iperf
> >>>>
> >>>> On 15/12/15 03:46, Bhushan Bharat wrote:
> >>>>>
> >>>>> Hi All,
> >>>>>
> >>>>> I am running "iperf" in KVM guest on ARM64 machine and observing
> >>>>> below
> >>>> crash.
> >>>>>
> >>>>> =============================
> >>>>> $iperf -c 3.3.3.3 -P 4 -t 0 -i 5 -w 90k
> >>>>> ------------------------------------------------------------
> >>>>> Client connecting to 3.3.3.3, TCP port 5001 TCP window size:  180
> >>>>> KByte (WARNING: requested 90.0 KByte)
> >>>>> ------------------------------------------------------------
> >>>>> [  3] local 3.3.3.1 port 51131 connected with 3.3.3.3 port 5001 [
> >>>>> 6] local 3.3.3.1 port 51134 connected with 3.3.3.3 port 5001 [  5]
> >>>>> local
> >>>>> 3.3.3.1 port 51133 connected with 3.3.3.3 port 5001 [  4] local
> >>>>> 3.3.3.1 port 51132 connected with 3.3.3.3 port 5001
> >>>>> [   53.088567] random: nonblocking pool is initialized
> >>>>> [ ID] Interval       Transfer     Bandwidth
> >>>>> [  3]  0.0- 5.0 sec   638 MBytes  1.07 Gbits/sec
> >>>>> [  4] 35.0-40.0 sec  1.66 GBytes  2.85 Gbits/sec [  5] 40.0-45.0
> >>>>> sec
> >>>>> 1.11 GBytes  1.90 Gbits/sec [  4] 40.0-45.0 sec  1.16 GBytes  1.99
> >>>>> Gbits/sec
> >>>>> [   98.895207] BUG: Bad page state in process iperf  pfn:0a584
> >>>>> [   98.896164] page:ffff780000296100 count:-1 mapcount:0 mapping:
> >>>> (null) index:0x0
> >>>>> [   98.897436] flags: 0x0()
> >>>>> [   98.897885] page dumped because: nonzero _count
> >>>>> [   98.898640] Modules linked in:
> >>>>> [   98.899178] CPU: 0 PID: 1639 Comm: iperf Not tainted 4.1.8-00461-
> >>>> ge5431ad #141
> >>>>> [   98.900302] Hardware name: linux,dummy-virt (DT)
> >>>>> [   98.901014] Call trace:
> >>>>> [   98.901406] [<ffff800000096cac>] dump_backtrace+0x0/0x12c
> >>>>> [   98.902522] [<ffff800000096de8>] show_stack+0x10/0x1c
> >>>>> [   98.903441] [<ffff800000678dc8>] dump_stack+0x8c/0xdc
> >>>>> [   98.904202] [<ffff800000145480>] bad_page+0xc4/0x114
> >>>>> [   98.904945] [<ffff8000001487a4>]
> >> get_page_from_freelist+0x590/0x63c
> >>>>> [   98.905871] [<ffff80000014893c>]
> >> __alloc_pages_nodemask+0xec/0x794
> >>>>> [   98.906791] [<ffff80000059fc80>] skb_page_frag_refill+0x70/0xa8
> >>>>> [   98.907678] [<ffff80000059fcd8>] sk_page_frag_refill+0x20/0xd0
> >>>>> [   98.908550] [<ffff8000005edc04>] tcp_sendmsg+0x1f8/0x9a8
> >>>>> [   98.909368] [<ffff80000061419c>] inet_sendmsg+0x5c/0xd0
> >>>>> [   98.910178] [<ffff80000059bb44>] sock_sendmsg+0x14/0x58
> >>>>> [   98.911027] [<ffff80000059bbec>] sock_write_iter+0x64/0xbc
> >>>>> [   98.912119] [<ffff80000019b5b8>] __vfs_write+0xac/0x10c
> >>>>> [   98.913126] [<ffff80000019bcb8>] vfs_write+0x90/0x1a0
> >>>>> [   98.913963] [<ffff80000019c53c>] SyS_write+0x40/0xa0
> >>>>
> >>>> This looks quite bad, but I don't see anything here that links it
> >>>> to KVM (apart from being a guest). Do you have any indication that
> >>>> this is due to KVM misbehaving?
> >>>
> >>> I never observed this issue in host Linux but observed this issue
> >>> always in
> >> guest Linux. This issue does not comes immediately after I run
> >> "iperf" but after some time.
> >>>
> >>>> I'd appreciate a few more details.
> >>>
> >>> We have a networking hardware and we are directly assigning the h/w
> >>> to
> >> guest. When using the same networking hardware in host it always
> >> works as expected (tried 100s of times).
> >>> Also this issue is not observed when we have only one vCPU in guest
> >>> but
> >> seen when we have SMP guest.
> >>
> >> Can you reproduce the same issue without VFIO (using virtio, for
> example)?
> >
> > With virtio I have not observed this issue.
> >
> >> Is that platform VFIO? or PCI?
> >
> > It is not vfio-pci and vfio-platform. It is vfio-fls-mc (some
> > Freescale new hardware), similar to the lines of vfio-platform uses
> > same set of VFIO APIs used by vfio-pci/platform. Do you think this can
> > be some h/w specific issue.
> 
> I have no idea, but by the look of it, something could be doing DMA on top of
> your guest page tables, which is not really expected. I suggest you carefully
> look at:
> 
> 1) the DMA addresses that are passed to your device
> 2) the page tables that are programmed into the SMMU
> 3) the resulting translation

Thanks Mark, this is good info. I will continue debugging keeping these points in my mind.

-Bharat

> 
> Hopefully this will give you a clue about what is generating this.
> 
> Thanks,
> 
> 	M.
> --
> Jazz is not dead. It just smells funny...