On 04/11/2012 02:03 PM, Steven wrote: > Hi, Guangrong, > I read your very nice slides at LCJ 2011, "KVM MMU virtualization". > However, I have some confusion about nested paging, > which you gave a simplified example to illustrate in slide 11. > The very first step is to use gCR3 as the input to the nested page I remember that i did not mention nested mmu in my presentation, the illustrate is about shadow mmu. > walk. So you mark gCR3 as the guest physical address (gpa). > So my first question is whether gCR3 is exactly the GPA as the input > to the nested paging? No, on nested mmu, the guest page table is from nested guest's vmcb.nested_cr3/vmcs.eptp which translates nested guest's gpa to L1 guest's gpa. > > Then after the nested page walk, we can have hpa. Now suppose we > use the first 10 bit of the gva to combine with the hpa to find the > guest table entry. Here is this step like traditional x86 paging, > ie.., hpa as the base to the guest page directory (guest page table > page) and gva is the offset? gva -> gpa The npt/ept table is walked base on gpa. > If so, I feel that this is contradict to figure 1(b) of the paper > "Accelerating Two-Dimensional Page Walks for Virtualized Systems". In > this paper, gva is used at the very beginning to combine with gCR3 to > generate a GPA, instead of after the nested paging. gCR3 stores the page table to translate gva to gpa on guest. And npt/ept table translate gpa to pfn, and the table is established by host. I find a paper on google, hope it is useful for you: http://researcher.ibm.com/files/us-bbfinkel/turtles_paper.pdf -- 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
