Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > ----- Original Message ----- >> From: "Bandan Das" <bsd@xxxxxxxxxx> >> To: "Paolo Bonzini" <pbonzini@xxxxxxxxxx> >> Cc: linux-kernel@xxxxxxxxxxxxxxx, kvm@xxxxxxxxxxxxxxx, david@xxxxxxxxxx >> Sent: Wednesday, April 12, 2017 7:35:16 AM >> Subject: Re: [PATCH 4/6] kvm: nVMX: support EPT accessed/dirty bits >> >> Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: >> ... >> > accessed_dirty = have_ad ? PT_GUEST_ACCESSED_MASK : 0; >> > + >> > + /* >> > + * FIXME: on Intel processors, loads of the PDPTE registers for PAE >> > paging >> > + * by the MOV to CR instruction are treated as reads and do not cause the >> > + * processor to set the dirty flag in tany EPT paging-structure entry. >> > + */ >> >> Minor typo: "in any EPT paging-structure entry". >> >> > + nested_access = (have_ad ? PFERR_WRITE_MASK : 0) | PFERR_USER_MASK; >> > + >> > pt_access = pte_access = ACC_ALL; >> > ++walker->level; >> > >> > @@ -338,7 +337,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker >> > *walker, >> > walker->pte_gpa[walker->level - 1] = pte_gpa; >> > >> > real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn), >> > - PFERR_USER_MASK|PFERR_WRITE_MASK, >> > + nested_access, >> > &walker->fault); >> >> I can't seem to understand the significance of this change (or for that >> matter what was before this change). >> >> mmu->translate_gpa() just returns gfn_to_gpa(table_gfn), right ? > > For EPT it is, you're right it's fishy. The "nested_access" should be > computed in translate_nested_gpa, which is where kvm->arch.nested_mmu > (non-EPT) requests to access kvm->arch.mmu (EPT). Thanks for the clarification. Is it the case when L1 runs L2 without EPT ? I can't figure out the case where translate_nested_gpa will actually be called. FNAME(walk_addr_nested) calls walk_addr_generic with &vcpu->arch.nested_mmu and init_kvm_nested_mmu() sets gva_to_gpa() with the appropriate "_nested" functions. But the gva_to_gpa() pointers don't seem to get invoked at all for the nested case. BTW, just noticed that setting PFERR_USER_MASK is redundant since translate_nested_gpa does it too. Bandan > In practice we need to define a new function > vcpu->arch.mmu.gva_to_gpa_nested that computes the nested_access > and calls cpu->arch.mmu.gva_to_gpa. > > Thanks, > > Paolo
