Hi,
Be warned: Though my experience is already more than a year old, the SVM
emulation in QEMU is most probably not yet rock-stable. Always check
suspicious behavior against real hardware and/or the spec. [ As real
hardware is everywhere, nesting works with KVM+SVM and is much faster,
motivation to improve QEMU in this area is unfortunately limited. ]
Problem is: I'm compiling in Linux and testing in MINIX. Testing on the
real hardware would require a reboot everytime. Moreover, it might screw
up my system if I make bad mistakes (the MINIX filesystem is easily
corrupted).
That said, I do aim to eventually test the real hardware. Plenty of
virtualization capable hardware where I work, although unfortunately all
Intel.
This issue is easy to work around by clearing the EVENTINJ field on each
#VMEXIT (and I have submitted a patch to that effect to the Palacios
people) and this approach is also found in KVM.
/me does not find such clearing in KVM - what line(s) are you looking at?
Linux source tree (2.6.31-ubuntu), arch/x86/kvm/svm.c, end of function
nested_svm_vmrun. Here event_inj and event_inj_err are copied from a
different VMCB, effectively clearing the value set by the CPU. Maybe
this isn't were I should have been looking though?
The relevant code is in target-i386/op_helper.c. The "handle_even_inj"
function sets the EVENTINJ field (called event_inf in the QEMU code) and
the helper_vmexit function copies that field into EXITINTINFO
(exit_int_info in the QEMU code). I believe (but once again, am not
certain) that the SVM documentation only says that this information
should be stored in EXITINTINFO.
Yes, this also looks suspicious. handle_even_inj should not push the
real (level 1) event to be injected into event_inj[_err] but into
exit_int_info[_err] or some temporary fields from which the exit info is
then loaded later on.
Yes, if this is indeed incorrect behaviour then this is what I would
expect a fix to be like.
Thanks again,
Erik
