Re: [Qemu-devel] [KVM] segmentation fault happened when reboot VM after hot-uplug virtio NIC

[Gleb Natapov <gleb@redhat.com>]

On Tue, Sep 03, 2013 at 12:06:33PM +0000, Zhanghaoyu (A) wrote:
> Hi, all
> 
> Segmentation fault happened when reboot VM after hot-unplug virtio NIC, which can be reproduced 100%.
> See similar bug report to https://bugzilla.redhat.com/show_bug.cgi?id=988256
> 
> test environment:
> host: SLES11SP2 (kenrel version: 3.0.58)
> qemu: 1.5.1, upstream-qemu (commit 545825d4cda03ea292b7788b3401b99860efe8bc)
> libvirt: 1.1.0
> guest os: win2k8 R2 x64bit or sles11sp2 x64 or win2k3 32bit
> 
> You can reproduce this problem by following steps:
> 1. start a VM with virtio NIC(s)
> 2. hot-unplug a virtio NIC from the VM
> 3. reboot the VM, then segmentation fault happened during starting period
> 
> the qemu backtrace shown as below:
> #0  0x00007ff4be3288d0 in __memcmp_sse4_1 () from /lib64/libc.so.6
> #1  0x00007ff4c07f82c0 in patch_hypercalls (s=0x7ff4c15dd610) at /mnt/zhanghaoyu/qemu/qemu-1.5.1/hw/i386/kvmvapic.c:549
> #2  0x00007ff4c07f84f0 in vapic_prepare (s=0x7ff4c15dd610) at /mnt/zhanghaoyu/qemu/qemu-1.5.1/hw/i386/kvmvapic.c:614
> #3  0x00007ff4c07f85e7 in vapic_write (opaque=0x7ff4c15dd610, addr=0, data=32, size=2)
>     at /mnt/zhanghaoyu/qemu/qemu-1.5.1/hw/i386/kvmvapic.c:651
> #4  0x00007ff4c082a917 in memory_region_write_accessor (opaque=0x7ff4c15df938, addr=0, value=0x7ff4bbfe3d00, size=2, 
>     shift=0, mask=65535) at /mnt/zhanghaoyu/qemu/qemu-1.5.1/memory.c:334
> #5  0x00007ff4c082a9ee in access_with_adjusted_size (addr=0, value=0x7ff4bbfe3d00, size=2, access_size_min=1, 
>     access_size_max=4, access=0x7ff4c082a89a <memory_region_write_accessor>, opaque=0x7ff4c15df938)
>     at /mnt/zhanghaoyu/qemu/qemu-1.5.1/memory.c:364
> #6  0x00007ff4c082ae49 in memory_region_iorange_write (iorange=0x7ff4c15dfca0, offset=0, width=2, data=32)
>     at /mnt/zhanghaoyu/qemu/qemu-1.5.1/memory.c:439
> #7  0x00007ff4c08236f7 in ioport_writew_thunk (opaque=0x7ff4c15dfca0, addr=126, data=32)
>     at /mnt/zhanghaoyu/qemu/qemu-1.5.1/ioport.c:219
> #8  0x00007ff4c0823078 in ioport_write (index=1, address=126, data=32) at /mnt/zhanghaoyu/qemu/qemu-1.5.1/ioport.c:83
> #9  0x00007ff4c0823ca9 in cpu_outw (addr=126, val=32) at /mnt/zhanghaoyu/qemu/qemu-1.5.1/ioport.c:296
> #10 0x00007ff4c0827485 in kvm_handle_io (port=126, data=0x7ff4c0510000, direction=1, size=2, count=1)
>     at /mnt/zhanghaoyu/qemu/qemu-1.5.1/kvm-all.c:1485
> #11 0x00007ff4c0827e14 in kvm_cpu_exec (env=0x7ff4c15bf270) at /mnt/zhanghaoyu/qemu/qemu-1.5.1/kvm-all.c:1634
> #12 0x00007ff4c07b6f27 in qemu_kvm_cpu_thread_fn (arg=0x7ff4c15bf270) at /mnt/zhanghaoyu/qemu/qemu-1.5.1/cpus.c:759
> #13 0x00007ff4be58af05 in start_thread () from /lib64/libpthread.so.0
> #14 0x00007ff4be2cd53d in clone () from /lib64/libc.so.6
> 
> If I apply below patch to the upstream qemu, this problem will disappear,
> ---
>  hw/i386/kvmvapic.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
> index 15beb80..6fff299 100644
> --- a/hw/i386/kvmvapic.c
> +++ b/hw/i386/kvmvapic.c
> @@ -652,11 +652,11 @@ static void vapic_write(void *opaque, hwaddr addr, uint64_t data,
>      switch (size) {
>      case 2:
>          if (s->state == VAPIC_INACTIVE) {
> -            rom_paddr = (env->segs[R_CS].base + env->eip) & ROM_BLOCK_MASK;
> -            s->rom_state_paddr = rom_paddr + data;
> -
>              s->state = VAPIC_STANDBY;
>          }
> +        rom_paddr = (env->segs[R_CS].base + env->eip) & ROM_BLOCK_MASK;
> +        s->rom_state_paddr = rom_paddr + data;
> +
Jan, does this mean that vapic state dies not move to inactive during
reset?

>          if (vapic_prepare(s) < 0) {
>              s->state = VAPIC_INACTIVE;
>              break;
> --
> 1.8.1.4
> 
> Thanks,
> Daniel
> 
> 

--
			Gleb.