From: Bhushan Bharat <Bharat.Bhushan@freescale.com>
To: Marc Zyngier <marc.zyngier@arm.com>,
        "kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: ARM64/KVM: Bad page state in process iperf
Thread-Topic: ARM64/KVM: Bad page state in process iperf
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Date: Tue, 15 Dec 2015 09:53:32 +0000
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Hi Mark,

> -----Original Message-----
> From: Marc Zyngier [mailto:marc.zyngier@arm.com]
> Sent: Tuesday, December 15, 2015 3:05 PM
> To: Bhushan Bharat-R65777 <Bharat.Bhushan@freescale.com>;
> kvmarm@lists.cs.columbia.edu; kvm@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; linux-kernel@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. 

Thanks
-Bharat

> 
> Thanks,
> 
> 	M.
> --
> Jazz is not dead. It just smells funny...
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