Alexander Graf wrote:
Hi,
I'm still trying to implement SVM correctly and hit a serious problem.
If I set CC_OP to EFLAGS / DYNAMIC after each instruction (so most
conditional operations are based on EFLAGS) everything works as expected.
If using CC_OP==CC_OP_EFLAGS only CC_SRC should be used and CC_DST is
supposed to be completely ignored.
So I set CC_DST to 0 (this happens when leaving and rejoining the
virtual machine, so this is the real problem) and if I do that, I get
funny segmentation faults in x86_64 guest userspace programs running in
the virtual machine (this is exactly what I see in kvm with my current
patchset as well), while 32 bit userspace programs simply hang.
So I guess this is the real problem.
Is there any logical reason CC_DST could be used with CC_OP==CC_OP_EFLAGS?
Attached to this email you will find a small patch that triggers this
problem.
Thanks for any reply that could help on this,
Alexander Graf
If you play with the CC_OP logic, it is better to disable the eflags
optimization code in the translator (optimize_flags() function).
Regarding the implementation for SVM, you can look at how the CC are
handled in SMM (do_smm_enter and helper_rsm). I see no particular
problem here.
I suggest to try to suppress the additions in the static translator
state as I feel most of the SVM intercepts can be tested in helpers
where speed is not critical.
Regards,
Fabrice.
