Re: [PATCH] KVM: nVMX: cleanup and fix host 64-bit mode checks

[Krish Sadhukhan]

On 09/25/2019 09:47 AM, Jim Mattson wrote:
> On Wed, Sep 25, 2019 at 9:34 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> > KVM was incorrectly checking vmcs12->host_ia32_efer even if the "load
> > IA32_EFER" exit control was reset.  Also, some checks were not using
> > the new CC macro for tracing.
> >
> > Cleanup everything so that the vCPU's 64-bit mode is determined
> > directly from EFER_LMA and the VMCS checks are based on that, which
> > matches section 26.2.4 of the SDM.
> >
> > Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > Cc: Jim Mattson <jmattson@xxxxxxxxxx>
> > Cc: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
> > Fixes: 5845038c111db27902bc220a4f70070fe945871c
> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > ---
> >   arch/x86/kvm/vmx/nested.c | 53 ++++++++++++++++++++---------------------------
> >   1 file changed, 22 insertions(+), 31 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > index 70d59d9304f2..e108847f6cf8 100644
> > --- a/arch/x86/kvm/vmx/nested.c
> > +++ b/arch/x86/kvm/vmx/nested.c
> > @@ -2664,8 +2664,26 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
> >              CC(!kvm_pat_valid(vmcs12->host_ia32_pat)))
> >                  return -EINVAL;
> >
> > -       ia32e = (vmcs12->vm_exit_controls &
> > -                VM_EXIT_HOST_ADDR_SPACE_SIZE) != 0;
> > +#ifdef CONFIG_X86_64
> > +       ia32e = !!(vcpu->arch.efer & EFER_LMA);
> > +#else
> > +       if (CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE))
> > +               return -EINVAL;
> This check is redundant, since it is checked in the else block below.

Should we be re-using is_long_mode() instead of duplicating the code ?

> > +
> > +       ia32e = false;
> > +#endif
> > +
> > +       if (ia32e) {
> > +               if (CC(!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)) ||
> > +                   CC(!(vmcs12->host_cr4 & X86_CR4_PAE)))
> > +                       return -EINVAL;
> > +       } else {
> > +               if (CC(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) ||
> > +                   CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
> > +                   CC(vmcs12->host_cr4 & X86_CR4_PCIDE) ||
> > +                   CC(((vmcs12->host_rip) >> 32) & 0xffffffff))
> The mask shouldn't be necessary.
>
> > +                       return -EINVAL;
> > +       }
> >
> >          if (CC(vmcs12->host_cs_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK)) ||
> >              CC(vmcs12->host_ss_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK)) ||
> > @@ -2684,35 +2702,8 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
> >              CC(is_noncanonical_address(vmcs12->host_gs_base, vcpu)) ||
> >              CC(is_noncanonical_address(vmcs12->host_gdtr_base, vcpu)) ||
> >              CC(is_noncanonical_address(vmcs12->host_idtr_base, vcpu)) ||
> > -           CC(is_noncanonical_address(vmcs12->host_tr_base, vcpu)))
> > -               return -EINVAL;
> > -
> > -       if (!(vmcs12->host_ia32_efer & EFER_LMA) &&
> > -           ((vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
> > -           (vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE))) {
> > -               return -EINVAL;
> > -       }
> > -
> > -       if ((vmcs12->host_ia32_efer & EFER_LMA) &&
> > -           !(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)) {
> > -               return -EINVAL;
> > -       }
> > -
> > -       if (!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) &&
> > -           ((vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
> > -           (vmcs12->host_cr4 & X86_CR4_PCIDE) ||
> > -           (((vmcs12->host_rip) >> 32) & 0xffffffff))) {
> > -               return -EINVAL;
> > -       }
> > -
> > -       if ((vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) &&
> > -           ((!(vmcs12->host_cr4 & X86_CR4_PAE)) ||
> > -           (is_noncanonical_address(vmcs12->host_rip, vcpu)))) {
> > -               return -EINVAL;
> > -       }
> > -#else
> > -       if (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE ||
> > -           vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)
> > +           CC(is_noncanonical_address(vmcs12->host_tr_base, vcpu)) ||
> > +           CC(is_noncanonical_address(vmcs12->host_rip, vcpu)))
> >                  return -EINVAL;
> >   #endif
> >
> > --
> > 1.8.3.1
> Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>