Re: [PATCH 2/2 v2]kvm-unit-test: nVMX: Test Host Segment Registers and Descriptor Tables on vmentry of nested guests

[Sean Christopherson <sean.j.christopherson@intel.com>]

On Sun, Jul 21, 2019 at 11:26:24AM -0700, Nadav Amit wrote:
> > On Jul 3, 2019, at 4:54 PM, Krish Sadhukhan <krish.sadhukhan@oracle.com> wrote:
> > 
> > According to section "Checks on Host Segment and Descriptor-Table
> > Registers" in Intel SDM vol 3C, the following checks are performed on
> > vmentry of nested guests:
> > 
> >    - In the selector field for each of CS, SS, DS, ES, FS, GS and TR, the
> >      RPL (bits 1:0) and the TI flag (bit 2) must be 0.
> >    - The selector fields for CS and TR cannot be 0000H.
> >    - The selector field for SS cannot be 0000H if the "host address-space
> >      size" VM-exit control is 0.
> >    - On processors that support Intel 64 architecture, the base-address
> >      fields for FS, GS, GDTR, IDTR, and TR must contain canonical
> >      addresses.
> 
> As I noted on v1, this patch causes the test to fail on bare-metal:
> 
>  FAIL: HOST_SEL_SS 0: VMX inst error is 8 (actual 7)
> 
> I don’t know what the root-cause is, but I don't think that tests that
> fail on bare-metal (excluding because of CPU errata) should be included.

A 64-bit VMM isn't allowed to transition to 32-bit mode by way of VM-Exit,
and the VMX tests are 64-bit only.

  If the logical processor is in IA-32e mode (if IA32_EFER.LMA=1) at the
  time of VM entry, the "host address space size" VM-exit control must be 1.