Re: KVM: VMX: fix incorrect cached cpl value with real/v8086 modes (v3)

Gleb Natapov
2013-01-08T10:56:55Z

On Mon, Jan 07, 2013 at 07:27:06PM -0200, Marcelo Tosatti wrote:
>
> CPL is always 0 when in real mode, and always 3 when virtual 8086 mode.
>
> Using values other than those can cause failures on operations that
> check CPL.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>
Reviewed-by: Gleb Natapov <gleb@redhat.com>

> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 55dfc37..dd2a85c 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1696,7 +1696,6 @@ static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu)
> static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
> {
> __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail);
> - __clear_bit(VCPU_EXREG_CPL, (ulong *)&vcpu->arch.regs_avail);
> to_vmx(vcpu)->rflags = rflags;
> if (to_vmx(vcpu)->rmode.vm86_active) {
> to_vmx(vcpu)->rmode.save_rflags = rflags;
> @@ -3110,7 +3109,6 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
> vmcs_writel(CR0_READ_SHADOW, cr0);
> vmcs_writel(GUEST_CR0, hw_cr0);
> vcpu->arch.cr0 = cr0;
> - __clear_bit(VCPU_EXREG_CPL, (ulong *)&vcpu->arch.regs_avail);
> }
>
> static u64 construct_eptp(unsigned long root_hpa)
> @@ -3220,8 +3218,10 @@ static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg)
> return vmx_read_guest_seg_base(to_vmx(vcpu), seg);
> }
>
> -static int __vmx_get_cpl(struct kvm_vcpu *vcpu)
> +static int vmx_get_cpl(struct kvm_vcpu *vcpu)
> {
> + struct vcpu_vmx *vmx = to_vmx(vcpu);
> +
> if (!is_protmode(vcpu))
> return 0;
>
> @@ -3229,13 +3229,6 @@ static int __vmx_get_cpl(struct kvm_vcpu *vcpu)
> && (kvm_get_rflags(vcpu) & X86_EFLAGS_VM)) /* if virtual 8086 */
> return 3;
>
> - return vmx_read_guest_seg_selector(to_vmx(vcpu), VCPU_SREG_CS) & 3;
> -}
> -
> -static int vmx_get_cpl(struct kvm_vcpu *vcpu)
> -{
> - struct vcpu_vmx *vmx = to_vmx(vcpu);
> -
> /*
> * If we enter real mode with cs.sel & 3 != 0, the normal CPL calculations
> * fail; use the cache instead.
> @@ -3246,7 +3239,7 @@ static int vmx_get_cpl(struct kvm_vcpu *vcpu)
>
> if (!test_bit(VCPU_EXREG_CPL, (ulong *)&vcpu->arch.regs_avail)) {
> __set_bit(VCPU_EXREG_CPL, (ulong *)&vcpu->arch.regs_avail);
> - vmx->cpl = __vmx_get_cpl(vcpu);
> + vmx->cpl = vmx_read_guest_seg_selector(vmx, VCPU_SREG_CS) & 3;
> }
>
> return vmx->cpl;

--
Gleb.