Radim Krčmář <rkrcmar@xxxxxxxxxx> writes: > 2017-07-17 13:58-0400, Bandan Das: >> Radim Krčmář <rkrcmar@xxxxxxxxxx> writes: >> ... >>>> > and no other mentions of a VM exit, so I think that the VM exit happens >>>> > only under these conditions: >>>> > >>>> > — The EPT memory type (bits 2:0) must be a value supported by the >>>> > processor as indicated in the IA32_VMX_EPT_VPID_CAP MSR (see >>>> > Appendix A.10). >>>> > — Bits 5:3 (1 less than the EPT page-walk length) must be 3, indicating >>>> > an EPT page-walk length of 4; see Section 28.2.2. >>>> > — Bit 6 (enable bit for accessed and dirty flags for EPT) must be 0 if >>>> > bit 21 of the IA32_VMX_EPT_VPID_CAP MSR (see Appendix A.10) is read >>>> > as 0, indicating that the processor does not support accessed and >>>> > dirty flags for EPT. >>>> > — Reserved bits 11:7 and 63:N (where N is the processor’s >>>> > physical-address width) must all be 0. >>>> > >>>> > And it looks like we need parts of nested_ept_init_mmu_context() to >>>> > properly handle VMX_EPT_AD_ENABLE_BIT. >>>> >>>> I completely ignored AD and the #VE sections. I will add a TODO item >>>> in the comment section. >>> >>> AFAIK, we don't support #VE, but AD would be nice to handle from the >>> beginning. (I think that caling nested_ept_init_mmu_context() as-is >>> isn't that bad.) >> >> I went back to the spec to take a look at the AD handling. It doesn't look >> like anything needs to be done since nested_ept_init_mmu_context() is already >> being called with the correct eptp in prepare_vmcs02 ? Anything else that >> needs to be done for AD handling in vmfunc context ? > > AD is decided by EPTP bit 6, so it can be toggled by EPTP switching and > we don't call prepare_vmcs02() after emulating VMFUNC vm exit. > We want to forward the new AD configuration to KVM's MMU. Thanks, I had incorrectly assumed that prepare_vmcs02 will be called after an exit unconditionally. I will work something up soon. Bandan
