Re: [Xen-devel] frequently ballooning results in qemu exit

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On 14/03/13 10:17, George Dunlap wrote:
> On Wed, Mar 13, 2013 at 1:50 PM, Hanweidong <hanweidong@xxxxxxxxxx> wrote:
>> We created a 64bit SLES11 SP1 guest, and then used a script to change memory 
>> (using mem-set command) periodically (in 1 second): set 1G, set 2G, set 1G, 
>> set 2G, and so on.
>> After a few minutes, we encountered QEMU exit due to SIGBUS error. Below is 
>> the call trace captured by gdb:
>>
>> The call trace:
>> Program received signal SIGBUS, Bus error.
>> 0x00007f94f74773d7 in memcpy () from /lib64/libc.so.6
>> (gdb) bt
>> #0  0x00007f94f74773d7 in memcpy () from /lib64/libc.so.6
>> #1  0x00007f94fa67016d in address_space_rw (as=<optimized out>, 
>> addr=2042531840, buf=0x7fffa36accf8 "", len=4, is_write=true) at 
>> /usr/include/bits/string3.h:52
>> #2  0x00007f94fa747cf0 in rw_phys_req_item (rw=<optimized out>, 
>> val=<optimized out>, i=<optimized out>, req=<optimized out>, addr=<optimized 
>> out>)
>>     at /opt/new/tools/qemu-xen-dir/xen-all.c:709
>> #3  write_phys_req_item (val=<optimized out>, i=<optimized out>, 
>> req=<optimized out>, addr=<optimized out>) at 
>> /opt/new/tools/qemu-xen-dir/xen-all.c:720
>> #4  cpu_ioreq_pio (req=<optimized out>) at 
>> /opt/new/tools/qemu-xen-dir/xen-all.c:736
>> #5  handle_ioreq (req=0x7f94fa464000) at 
>> /opt/new/tools/qemu-xen-dir/xen-all.c:793
>> #6  0x00007f94fa748abe in cpu_handle_ioreq (opaque=0x7f94fb39d3f0) at 
>> /opt/new/tools/qemu-xen-dir/xen-all.c:868
>> #7  0x00007f94fa5e3262 in qemu_iohandler_poll (readfds=0x7f94faeea7a0 
>> <rfds>, writefds=0x7f94faeea820 <wfds>, xfds=<optimized out>, ret=<optimized 
>> out>) at iohandler.c:125
>> #8  0x00007f94fa5ec51d in main_loop_wait (nonblocking=<optimized out>) at 
>> main-loop.c:418
>> #9  0x00007f94fa6616dc in main_loop () at vl.c:1770
>> #10 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) 
>> at vl.c:3999
>>
>> It looks mapcache has something wrong because memcpy failed with the address 
>> from mapcache. Any ideas about this issue? Thanks!
> 
> Which version of Xen and qemu are you using?  In particular,
> qemu-upstream (aka qemu-xen) or qemu-traditional?  And what guest are
> you using?  Is there anything on the xen console (either via the
> serial port or 'xl dmesg')?
> 
> At first glance it looks like maybe qemu is trying to access, via the
> mapcache, pages which have been ballooned out.  But it seems like it
> should only be doing so in response to a guest request -- is this
> correct, Anthony?

Yes, this look like a guest IO request. One things I don't know is what
happen if there is guest addresses present in the mapcache that have
been balloon out, then but back in the guest, are those addresses in
mapcache still correct?

-- 
Anthony PERARD

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