[Xen-devel] Capturing CPL changes

["Emre Can Sezer" <ecsezer@xxxxxxxx>]

Hi, I've set up a 64-bit HVM guest and was wondering if there is anyway I
can determine when the privilege level escalates to 0.  My goal is to
determine when execution jumps to the guest kernel.  This includes
external interrupts as well as internal ones like system calls.

I've read through the source code especially vmx.c, vmcs.c and exit.S as
well as the intel documentation on vmx, yet I couldn't figure out if I can
set  the bitmap so that system calls cause a VMEXIT.

Is there a way I can capture whenever execution jumps into kernel?  I've
enabled MSR read/writes to cause VMEXIT's but even then I don't see a read
from VMX_SYSENTER_CS/EIP/ESP.  I don't know if setting the MSR_GS_BASE or
MSR_FS_BASE is any indication.

I'm thinking about setting the debug registers in the VM so that the
system call entry points trap into the VMM.

I appreciate any help or advice on the matter.

Thanks in advance,

John


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