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.
