Re: [Qemu-devel] [PATCH v4 0/6] spapr/xics: fix migration of older machine types

[Greg Kurz]

On Fri, 9 Jun 2017 12:28:13 +1000
David Gibson <address@hidden> wrote:

> On Thu, Jun 08, 2017 at 03:42:32PM +0200, Greg Kurz wrote:
> > I've provided answers for all comments from the v3 review that I 
> > deliberately
> > don't address in v4.  
> 
> I've merged patches 1-4.  5 & 6 I'm still reviewing.
> 

Cool. FYI, I forgot to mention that I only tested with KVM.

I'm now trying with TCG and I hit various guest crash on
the destination (using your ppc-for-2.10 branch WITHOUT
my patches):

cpu 0x0: Vector: 700 (Program Check) at [c0000000787ebae0]
    pc: c0000000002803c4: __fput+0x284/0x310
    lr: c000000000280258: __fput+0x118/0x310
    sp: c0000000787ebd60
   msr: 8000000000029033
  current = 0xc00000007cbab640
  paca    = 0xc000000007b80000   softe: 0        irq_happened: 0x01
    pid   = 1812, comm = gawk
kernel BUG at ../include/linux/fs.h:2399!
enter ? for help
[c0000000787ebdb0] c0000000000d7d84 task_work_run+0xe4/0x160
[c0000000787ebe00] c000000000018054 do_notify_resume+0xb4/0xc0
[c0000000787ebe30] c00000000000a730 ret_from_except_lite+0x5c/0x60
--- Exception: c00 (System Call) at 00003fff9026dd90
SP (3fffcb37b790) is in userspace
0:mon> 

or

cpu 0x0: Vector: 300 (Data Access) at [c00000007fff7490]
    pc: c0000000001ef768: free_pcppages_bulk+0x2b8/0x500
    lr: c0000000001ef524: free_pcppages_bulk+0x74/0x500
    sp: c00000007fff7710
   msr: 8000000000009033
   dar: c0000000807afc70
 dsisr: 40000000
  current = 0xc00000007c609190
  paca    = 0xc000000007b80000   softe: 0        irq_happened: 0x01
    pid   = 1631, comm = systemctl
enter ? for help
[c00000007fff77c0] c0000000001eff24 free_hot_cold_page+0x204/0x270
[c00000007fff7810] c0000000001f5848 __put_single_page+0x48/0x60
[c00000007fff7840] c00000000059ac50 skb_release_data+0xb0/0x180
[c00000007fff7880] c00000000059ae38 kfree_skb+0x58/0x130
[c00000007fff78c0] c00000000063f604 __udp4_lib_mcast_deliver+0x3d4/0x460
[c00000007fff7a50] c00000000063fb0c __udp4_lib_rcv+0x47c/0x770
[c00000007fff7b00] c0000000006023a8 ip_local_deliver_finish+0x148/0x310
[c00000007fff7b50] c0000000006026c4 ip_rcv_finish+0x154/0x420
[c00000007fff7bd0] c0000000005b1154 __netif_receive_skb_core+0x874/0xac0
[c00000007fff7cc0] c0000000005b30d4 netif_receive_skb+0x34/0xd0
[c00000007fff7d00] d000000000ef3c74 virtnet_poll+0x514/0x8a0 [virtio_net]
[c00000007fff7e10] c0000000005b3668 net_rx_action+0x1d8/0x310
[c00000007fff7ea0] c0000000000b0cc4 __do_softirq+0x154/0x330
[c00000007fff7f90] c0000000000251ac call_do_softirq+0x14/0x24
[c00000007fff3ef0] c000000000011be0 do_softirq+0xe0/0x110
[c00000007fff3f30] c0000000000b10e8 irq_exit+0xc8/0x110
[c00000007fff3f60] c0000000000117e8 __do_irq+0xb8/0x1c0
[c00000007fff3f90] c0000000000251d0 call_do_irq+0x14/0x24
[c00000007a94bac0] c000000000011990 do_IRQ+0xa0/0x120
[c00000007a94bb20] c00000000000a8b0 restore_check_irq_replay+0x2c/0x5c
--- Exception: 501 (Hardware Interrupt) at c000000000010f84 
arch_local_irq_restore+0x74/0x90
[c00000007a94be10] 000000000000000c (unreliable)
[c00000007a94be30] c00000000000a704 ret_from_except_lite+0x30/0x60
--- Exception: 501 (Hardware Interrupt) at 00003fffa04a2c28
SP (3ffff7f1bf60) is in userspace
0:mon> 

These doesn't seem to occur with QEMU master. I'll try to investigate.

> > 
> > v4: - some patches from v3 got merged
> >     - added some more preparatory cleanup in xics (patches 1,2)
> >     - merge cpu_setup() handler into realize() (patch 4)
> >     - see individual changelog for patches 3 and 6
> > 
> > v3: - preparatory cleanup in pnv (patch 1)
> >     - rework ICPState realization and vmstate registration (patches 2,3,4)
> >     - fix migration using dummy icp/server entries (patch 5)
> > 
> > v2: - some patches from v1 are already merged in ppc-for-2.10
> >     - added a new fix to a potential memory leak (patch 1)
> >     - consolidate dt_id computation (patch 3)
> >     - see individual changelogs for patch 2 and 4
> > 
> > I could successfully do the following on POWER8 host with full cores (SMT8):
> > 
> > 1) start a pseries-2.9 machine with QEMU 2.9:
> >         -smp cores=1,threads=2,maxcpus=8
> > 2) hotplug a core:
> >         device_add host-spapr-cpu-core,core-id=4
> > 3) migrate to QEMU 2.10 configured with core-id 0,4
> > 4) hotplug another core:
> >         device_add host-spapr-cpu-core,core-id=2
> > 5) migrate back to QEMU 2.9 configured with core-id 0,4,2
> > 6) hotplug the core in the last available slot:
> >         device_add host-spapr-cpu-core,core-id=6
> > 7) migrate to QEMU 2.10 configured with core-id 0,4,2,6
> > 
> > I could check that the guest is functional after each migration.
> >   
>

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