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

[Gleb Natapov]

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 
> 
Reviewed-by: Gleb Natapov 

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

[Marcelo Tosatti]

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 

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;
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