On Fri, Apr 29, 2022, Paolo Bonzini wrote: > On 4/29/22 16:42, Sean Christopherson wrote: > > On Fri, Apr 29, 2022, Paolo Bonzini wrote: > > > On 4/29/22 16:24, Sean Christopherson wrote: > > > > I don't love the divergent memslot behavior, but it's technically correct, so I > > > > can't really argue. Do we want to "officially" document the memslot behavior? > > > > > > > > > > I don't know what you mean by officially document, > > > > Something in kvm/api.rst under KVM_SET_USER_MEMORY_REGION. > > Not sure if the API documentation is the best place because userspace does > not know whether shadow paging is on (except indirectly through other > capabilities, perhaps)? Hrm, true, it's not like the userspace VMM can rewrite itself at runtime. > It could even be programmatic, such as returning 52 for CPUID[0x80000008]. > A nested KVM on L1 would not be able to use the #PF(RSVD) trick to detect > MMIO faults. That's not a big price to pay, however I'm not sure it's a > good idea in general... Agreed, messing with CPUID is likely to end in tears.
