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

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Date:   Wed, 25 Sep 2019 09:47:05 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Krish Sadhukhan <krish.sadhukhan@...cle.com>
Subject: Re: [PATCH] KVM: nVMX: cleanup and fix host 64-bit mode checks

On Wed, Sep 25, 2019 at 9:34 AM Paolo Bonzini <pbonzini@...hat.com> 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@...el.com>
> Cc: Jim Mattson <jmattson@...gle.com>
> Cc: Krish Sadhukhan <krish.sadhukhan@...cle.com>
> Fixes: 5845038c111db27902bc220a4f70070fe945871c
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  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.

> +
> +       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@...gle.com>