On Mon, Dec 28, 2015 at 6:25 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > > On 28/12/2015 23:23, David Matlack wrote: >> I'm wondering if this comment in mmu.c:init_kvm_nested_mmu is correct (at >> least in the context of Nested EPT): >> >> 4055 /* >> 4056 * Note that arch.mmu.gva_to_gpa translates l2_gva to l1_gpa. The >> 4057 * translation of l2_gpa to l1_gpa addresses is done using the >> 4058 * arch.nested_mmu.gva_to_gpa function. Basically the gva_to_gpa >> 4059 * functions between mmu and nested_mmu are swapped. >> 4060 */ >> >> nested_mmu.get_cr3 gets set to get_cr3, which I believe will return L2's cr3. >> In vmx.c:nested_ept_init_mmu_context, mmu.get_cr3 is set to >> nested_ept_get_cr3, which should be the root of EPT12. Given these get_cr3 >> functions, shouldn't nested_mmu.gva_to_gpa translate l2_gva->l2_gpa and I think I got this wrong. walk_addr_generic uses translate_gpa to convert the l2_gpa into its l1_gpa address at the end of the translation. So nested_mmu.gva_to_gpa should translate l2_gva to l1_gpa? >> mmu.gva_to_gpa translate l2_gpa->l1_gpa? > > Yes, it's correct. It can be trivially seen by looking at > kvm_init_shadow_ept_mmu's usage of &vcpu->arch.mmu. This is obviously a > l2_gpa to l1_gpa translation. If vcpu->arch.mmu.gva_to_gpa is a l2_gpa to l1_gpa translation, then the comment is incorrect... right? The comment says "arch.mmu.gva_to_gpa translates l2_gva to l1_gpa" and "l2_gpa to l1_gpa addresses is done using the arch.nested_mmu.gva_to_gpa". > > Whether the roles are swapped, depends on whether you think of > "nested_mmu" as "nested guest" or "nested virtualization" nested_mmu is > the MMU for the nested guest, mmu is the MMU for the L1 guest and it's > the one that takes care of nested virtualization. > > Paolo -- 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
