Jun Koi wrote: > On 10/1/07, Anthony Liguori <[EMAIL PROTECTED]> 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. >> >> 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. >> > > This is a bit vague to me. Why do you need "a piece of guest memory" here? >
You don't just need guest memory, you need a valid guest virtual address too. The IDTR contains a guest VA. If you want to create your own IDT, then it has to be a valid VA in the guest's address space. Regards, Anthony Liguori > Thanks, > Jun > > ------------------------------------------------------------------------- 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
