On Tue, Sep 11, 2012, siddhesh phadke wrote about "Multi-dimensional Paging in Nested virtualization": > I read turtles project paper where they have explained how > multi-dimensional page tables are built on L0. L2 is launched with > empty EPT 0->2 and EPT 0->2 is built on-the-fly. > I tried to find out how this is done in kvm code but i could not find > where EPT 0->2 is built. Nested EPT is not yet included in the mainline KVM. The original nested EPT code that we had written as part of the Turtles paper became obsolete when much of KVM's MMU code has been rewritten. I have since rewritten the nested EPT code for the modern KVM. I sent the second (latest) version of these patches to the KVM mailing list in August, and you can find them in, for example, http://comments.gmane.org/gmane.comp.emulators.kvm.devel/95395 These patches were not yet accepted into KVM. They have bugs in various setups (which I have not yet found the time to fix, unfortunately), and some known issues found by Avi Kivity on this mailing lest. > Does L1 handle ept violation first and then L0 updates its EPT0->2? > How this is done? This is explained in the turtles paper, but here's the short story: L1 defines an EPT table for L2 which we call EPT12. L0 builds from this an EPT02, with L1 addresses changed to L0. Now, when L2 runs and we get an EPT violation, we exit to L0 (in nested vmx, any exit first gets to L0). L0 checks if the translation is missing already in EPT12, and if it isn't it emulates an exit into L1 - and inject the EPT violation into L1. But if the translation wasn't missing in EPT12, then it's L0's problem, and we just need to update EPT02. > Can anybody give me some pointers about where to look into the code? Please look at the patches above. Each patch is also documented. Nadav. -- Nadav Har'El | Thursday, Sep 13 2012, 26 Elul 5772 nyh@xxxxxxxxxxxxxxxxxxx |----------------------------------------- Phone +972-523-790466, ICQ 13349191 |error compiling committee.c: too many http://nadav.harel.org.il |arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
