Re: [Qemu-devel] Ubuntu/Debian Installer + Virtio-SCSI -> Bad ram pointer

[Peter Lieven <pl@dlhnet.de>]

Am 30.10.2012 19:27, schrieb Stefan Hajnoczi:
> On Tue, Oct 30, 2012 at 4:56 PM, Peter Lieven <pl@dlhnet.de> wrote:
>> On 30.10.2012 09:32, Stefan Hajnoczi wrote:
>>> On Mon, Oct 29, 2012 at 03:09:37PM +0100, Peter Lieven wrote:
>>>> Hi,
>>> Bug subject should be virtio-blk, not virtio-scsi.  virtio-scsi is a
>>> different virtio device type from virtoi-blk and is not present in the
>>> backtrace you posted.
>>>
>>> Sounds pedantic but I want to make sure this gets chalked up against the
>>> right device :).
>>>
>>>> If I try to Install Ubuntu 12.04 LTS / 12.10 64-bit on a virtio
>>>> storage backend that supports iSCSI
>>>> qemu-kvm crashes reliably with the following error:
>>> Are you using vanilla qemu-kvm-1.2.0 or are there patches applied?
>>>
>>> Have you tried qemu-kvm.git/master?
>>>
>>> Have you tried a local raw disk image to check whether libiscsi is
>>> involved?
>>>
>>>> Bad ram pointer 0x3039303620008000
>>>>
>>>> This happens directly after the confirmation of the Timezone before
>>>> the Disk is partitioned.
>>>>
>>>> If I specify  -global virtio-blk-pci.scsi=off in the cmdline this
>>>> does not happen.
>>>>
>>>> Here is a stack trace:
>>>>
>>>> Thread 1 (Thread 0x7ffff7fee700 (LWP 8226)):
>>>> #0 0x00007ffff63c0a10 in abort () from /lib/x86_64-linux-gnu/libc.so.6
>>>> No symbol table info available.
>>>> #1 <https://github.com/sahlberg/libiscsi/issues/1>
>>>> 0x00005555557b751d in qemu_ram_addr_from_host_nofail (
>>>> ptr=0x3039303620008000) at /usr/src/qemu-kvm-1.2.0/exec.c:2835
>>>> ram_addr = 0
>>>> #2 <https://github.com/sahlberg/libiscsi/issues/2>
>>>> 0x00005555557b9177 in cpu_physical_memory_unmap (
>>>> buffer=0x3039303620008000, len=4986663671065686081, is_write=1,
>>>> access_len=1) at /usr/src/qemu-kvm-1.2.0/exec.c:3645
>>> buffer and len are ASCII junk.  It appears to be hex digits and it's not
>>> clear where they come from.
>>>
>>> It would be interesting to print *elem one stack frame up in #3
>>> virtqueue_fill() to show the iovecs and in/out counts.
>>
>> (gdb) print *elem
> Great, thanks for providing this info:
>
>> $6 = {index = 3, out_num = 2, in_num = 4, in_addr = {1914920960, 1916656688,
>>      2024130072, 2024130088, 0 <repeats 508 times>, 4129, 93825009696000,
>>      140737328183160, 0 <repeats 509 times>}, out_addr = {2024130056,
>>      2038414056, 0, 8256, 4128, 93824999311936, 0, 3, 0 <repeats 512 times>,
>>      12385, 93825009696000, 140737328183160, 0 <repeats 501 times>},
> Up to here everything is fine.
>
>> in_sg =
>> {{
>>        iov_base = 0x3039303620008000, iov_len = 4986663671065686081}, {
>>        iov_base = 0x3830384533334635, iov_len = 3544389261899019573}, {
> The fields are bogus, in_sg has been overwritten with ASCII data.
> Unfortunately I don't see any hint of where this ASCII data came from
> yet.
>
> The hdr fields you provided in stack frame #6 show that in_sg was
> overwritten during or after the bdrv_ioctl() call.  We pulled valid
> data out of the vring and mapped buffers correctly.  But something is
> overwriting in_sg and when we complete the request we blow up due to
> the bogus values.
>
> Please post your full qemu-kvm command-line.
>
> Please also post the exact qemu-kvm version you are using.  I can see
> it's based on qemu-kvm-1.2.0 but are there any patches applied (e.g.
> distro packages may carry patches so the full package version
> information would be useful)?
Stefan, Ronnie, if I do remove the following patch from my cherry-picked 
patches its
working again:

iSCSI: We need to support SG_IO also from iscsi_ioctl()

Peter