From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: KVM: VMX: fix incorrect cached cpl value with real/v8086 modes
 (v3)
Date: Tue, 8 Jan 2013 12:56:53 +0200
Message-ID: <20130108105653.GK21250@redhat.com>
References: <20121219132926.GA3551@amt.cnet>
 <20130103134957.GA3266@amt.cnet>
 <20130107212706.GB26134@amt.cnet>
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Cc: Avi Kivity <avi.kivity@gmail.com>, kvm <kvm@vger.kernel.org>
To: Marcelo Tosatti <mtosatti@redhat.com>
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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.