Anthony Liguori wrote: > Cam Macdonell wrote: >> Anthony Liguori wrote: >>> Cameron Macdonell wrote: >>>> Hi, >>>> >>>> I'm trying to understand guest virtualization at the lower levels. >>>> I have a somewhat basic question: How does KVM virtualize an >>>> int80 instruction from a guest? A pointer to an answer is just as >>>> good as an answer itself. >>>> >>> >>> The same thing happens as it does on normal hardware. >>> >>> The way VT/SVM works (at a high level), is that certain instructions >>> and events check a special area called the VMCS/VMCB to determine >>> whether the event should generate a vmexit which is really just a >>> special type of trap. >>> >> >> Thanks Anthony. Does an int80 from an application in the guest always >> cause a vmexit (in kvm's case at least)? > > No, an int80 would never generate a trap in KVM. The only way to make > it generate a trap is for an int80 to trigger some other event that > would generate a trap. This is what I meant by taking over the guest's > IDT such that you could change the int80 handler to do a hypercall. > > I presume you're looking into doing a guest IDS right? >
Actually, I looking into doing a PhD dissertation :) I'm just trying to get a better working understanding of how kvm (and other VMMs) handle instructions like int80 that should trap into the OS, but of course in a VM need to trap into the guest OS (which is running at user-level) and not the host OS. Do traps by a guest app to the guest OS involve the VMM at all? Pardon my ignorance, what is IDS? Thanks, Cam ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
