diff mbox series

[RFC,v4,4/8] KVM:VMX: Pass through host CET related MSRs to Guest.

Message ID 20190318150351.15550-5-weijiang.yang@intel.com (mailing list archive)
State New, archived
Headers show
Series This patch-set is to enable Guest CET support | expand

Commit Message

Yang, Weijiang March 18, 2019, 3:03 p.m. UTC 
The CET runtime settings, i.e., CET state control bits(IA32_U_CET/
IA32_S_CET), CET SSP(IA32_PL3_SSP/IA32_PL0_SSP) and SSP table address
(IA32_INTERRUPT_SSP_TABLE_ADDR) are task/thread specific, therefore,
OS needs to save/restore the states properly during context switch,
e.g., task/thread switching, interrupt/exception handling, it uses
xsaves/xrstors to achieve that.

The difference between VMCS CET area fields and xsave CET area, is that
the former is for state retention during Guest/Host context
switch while the latter is for state retention during OS execution.

Linux currently doesn't support CPL1 and CPL2, so SSPs for these level
are skipped here.

Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
 arch/x86/kvm/vmx.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

Comments

Sean Christopherson April 2, 2019, 8:27 p.m. UTC | #1 
On Mon, Mar 18, 2019 at 11:03:47PM +0800, Yang Weijiang wrote:
> The CET runtime settings, i.e., CET state control bits(IA32_U_CET/
> IA32_S_CET), CET SSP(IA32_PL3_SSP/IA32_PL0_SSP) and SSP table address
> (IA32_INTERRUPT_SSP_TABLE_ADDR) are task/thread specific, therefore,
> OS needs to save/restore the states properly during context switch,
> e.g., task/thread switching, interrupt/exception handling, it uses
> xsaves/xrstors to achieve that.
> 
> The difference between VMCS CET area fields and xsave CET area, is that
> the former is for state retention during Guest/Host context
> switch while the latter is for state retention during OS execution.
> 
> Linux currently doesn't support CPL1 and CPL2, so SSPs for these level
> are skipped here.
> 
> Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> ---
>  arch/x86/kvm/vmx.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 53cef5a3db96..28b8ac027bd7 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -11774,6 +11774,7 @@ static void nested_vmx_entry_exit_ctls_update(struct kvm_vcpu *vcpu)
>  static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> +	unsigned long *msr_bitmap;
>  
>  	if (cpu_has_secondary_exec_ctrls()) {
>  		vmx_compute_secondary_exec_control(vmx);
> @@ -11791,6 +11792,18 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
>  		nested_vmx_cr_fixed1_bits_update(vcpu);
>  		nested_vmx_entry_exit_ctls_update(vcpu);
>  	}
> +
> +	msr_bitmap = vmx->vmcs01.msr_bitmap;
> +
> +	if (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
> +	    guest_cpuid_has(vcpu, X86_FEATURE_IBT)) {
> +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_U_CET, MSR_TYPE_RW);
> +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_S_CET, MSR_TYPE_RW);
> +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW);
> +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL0_SSP, MSR_TYPE_RW);

I thought we had agreed to pass-through PL1 and PL2, or am I misremembering?

> +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL3_SSP, MSR_TYPE_RW);
> +	}
> +
>  }
>  
>  static void vmx_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
> -- 
> 2.17.1
>
Yang, Weijiang April 2, 2019, 8:46 p.m. UTC | #2 
On Tue, Apr 02, 2019 at 01:27:33PM -0700, Sean Christopherson wrote:
> On Mon, Mar 18, 2019 at 11:03:47PM +0800, Yang Weijiang wrote:
> > The CET runtime settings, i.e., CET state control bits(IA32_U_CET/
> > IA32_S_CET), CET SSP(IA32_PL3_SSP/IA32_PL0_SSP) and SSP table address
> > (IA32_INTERRUPT_SSP_TABLE_ADDR) are task/thread specific, therefore,
> > OS needs to save/restore the states properly during context switch,
> > e.g., task/thread switching, interrupt/exception handling, it uses
> > xsaves/xrstors to achieve that.
> > 
> > The difference between VMCS CET area fields and xsave CET area, is that
> > the former is for state retention during Guest/Host context
> > switch while the latter is for state retention during OS execution.
> > 
> > Linux currently doesn't support CPL1 and CPL2, so SSPs for these level
> > are skipped here.
> > 
> > Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
> > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> > ---
> >  arch/x86/kvm/vmx.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index 53cef5a3db96..28b8ac027bd7 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -11774,6 +11774,7 @@ static void nested_vmx_entry_exit_ctls_update(struct kvm_vcpu *vcpu)
> >  static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
> >  {
> >  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> > +	unsigned long *msr_bitmap;
> >  
> >  	if (cpu_has_secondary_exec_ctrls()) {
> >  		vmx_compute_secondary_exec_control(vmx);
> > @@ -11791,6 +11792,18 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
> >  		nested_vmx_cr_fixed1_bits_update(vcpu);
> >  		nested_vmx_entry_exit_ctls_update(vcpu);
> >  	}
> > +
> > +	msr_bitmap = vmx->vmcs01.msr_bitmap;
> > +
> > +	if (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
> > +	    guest_cpuid_has(vcpu, X86_FEATURE_IBT)) {
> > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_U_CET, MSR_TYPE_RW);
> > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_S_CET, MSR_TYPE_RW);
> > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW);
> > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL0_SSP, MSR_TYPE_RW);
> 
> I thought we had agreed to pass-through PL1 and PL2, or am I misremembering?
>
Thanks Sean! I missed your last comments on this patch, will add them in
next version.
> > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL3_SSP, MSR_TYPE_RW);
> > +	}
> > +
> >  }
> >  
> >  static void vmx_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
> > -- 
> > 2.17.1
> >
diff mbox series

Patch

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 53cef5a3db96..28b8ac027bd7 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11774,6 +11774,7 @@  static void nested_vmx_entry_exit_ctls_update(struct kvm_vcpu *vcpu)
 static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	unsigned long *msr_bitmap;
 
 	if (cpu_has_secondary_exec_ctrls()) {
 		vmx_compute_secondary_exec_control(vmx);
@@ -11791,6 +11792,18 @@  static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
 		nested_vmx_cr_fixed1_bits_update(vcpu);
 		nested_vmx_entry_exit_ctls_update(vcpu);
 	}
+
+	msr_bitmap = vmx->vmcs01.msr_bitmap;
+
+	if (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
+	    guest_cpuid_has(vcpu, X86_FEATURE_IBT)) {
+		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_U_CET, MSR_TYPE_RW);
+		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_S_CET, MSR_TYPE_RW);
+		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW);
+		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL0_SSP, MSR_TYPE_RW);
+		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL3_SSP, MSR_TYPE_RW);
+	}
+
 }
 
 static void vmx_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)