[Xen-bugs] [Bug 703] New: ioemu corrupts data

[bugzilla-daemon@xxxxxxxxxxxxxxxxxxx]

http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=703

           Summary: ioemu corrupts data
           Product: Xen
           Version: unstable
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: critical
          Priority: P2
         Component: HVM
        AssignedTo: xen-bugs@xxxxxxxxxxxxxxxxxxx
        ReportedBy: riel@xxxxxxxxxx


While running into bug #620 (x86-64 hangs when running 2 VMX domains), I
discovered that the ioemu code lies about IO completion to the guest OSes.

When the guest domain sends a write command to the disk, ioemu:
1) submits an asynchronous write in dom0
2) pretends that the disk IO completed and returns to the guest

This causes a system running into bug #620 to lose up to 30 seconds of data,
which can be a total disaster when running a database (that relies on
journaling and write ordering) inside a VT guest.  I had to blow away a 2.9GB
database because things just were not salvageable any more...


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