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. There are no hooks for interrupts 32-255 so the hardware operates as it normally would. If you're interested in getting a trap for int80 within KVM, you'll have to trap sidt/lidt and virtualize the IDT. You'll need to setup a fake IDT and have the int80 handler do a hypercall. This is complicated if the guest is using a fast-syscall mechanism. It may be a little challenging finding a piece of guest memory to take over that has a valid virtual mapping. To solve this in the general case, you'll need to have the guest be aware of a memory hole. If you can limit yourself to things like Linux and Windows, you can probably just rely on some memory within the BIOS area (both Linux and Windows always have valid mappings of the BIOS memory). If you need to enforce that int80s go to you, you'll need to write-protect this memory too. Regards, Anthony Liguori > 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/kvm-devel > > ------------------------------------------------------------------------- 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 [email protected] https://lists.sourceforge.net/lists/listinfo/kvm-devel
