[PATCH v5 0/3] CET fix patches for nested guest

[PATCH v5 0/3] CET fix patches for nested guest

[Yang Weijiang]

This patch series is to fix a few issues found during patch review and
testing on Linux, also including a patch to explictly disable CET support
in nested guest over Hyper-V(s).

change in v5:
- Changed condition to snapshot CET state to vmcs01 per Sean's feedback.
- Remove mixed fix code for MPX.


Yang Weijiang (3):
  KVM: nVMX: Sync L2 guest CET states between L1/L2
  KVM: nVMX: Set X86_CR4_CET in cr4_fixed1_bits if CET IBT is enabled
  KVM: nVMX: Add CET entry/exit load bits to evmcs unsupported list

 arch/x86/kvm/cpuid.c      |  1 -
 arch/x86/kvm/vmx/evmcs.c  |  4 ++--
 arch/x86/kvm/vmx/evmcs.h  |  6 ++++--
 arch/x86/kvm/vmx/nested.c | 30 ++++++++++++++++++++++++++++++
 arch/x86/kvm/vmx/vmx.c    |  1 +
 arch/x86/kvm/vmx/vmx.h    |  3 +++
 6 files changed, 40 insertions(+), 5 deletions(-)

-- 
2.26.2

[PATCH v5 1/3] KVM: nVMX: Sync L2 guest CET states between L1/L2

[Yang Weijiang]

These fields are rarely updated by L1 QEMU/KVM, sync them when L1 is trying to
read/write them and after they're changed. If CET guest entry-load bit is not
set by L1 guest, migrate them to L2 manaully.

Opportunistically remove one blank line in previous patch.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
 arch/x86/kvm/cpuid.c      |  1 -
 arch/x86/kvm/vmx/nested.c | 30 ++++++++++++++++++++++++++++++
 arch/x86/kvm/vmx/vmx.h    |  3 +++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index d191de769093..8692f53b8cd0 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -143,7 +143,6 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
 		}
 		vcpu->arch.guest_supported_xss =
 			(((u64)best->edx << 32) | best->ecx) & supported_xss;
-
 	} else {
 		vcpu->arch.guest_supported_xss = 0;
 	}
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 9728efd529a1..87beb1c034e1 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2516,6 +2516,13 @@ static void prepare_vmcs02_rare(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
 	vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_autoload.guest.nr);
 
 	set_cr4_guest_host_mask(vmx);
+
+	if (kvm_cet_supported() && vmx->nested.nested_run_pending &&
+	    (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE)) {
+		vmcs_writel(GUEST_SSP, vmcs12->guest_ssp);
+		vmcs_writel(GUEST_S_CET, vmcs12->guest_s_cet);
+		vmcs_writel(GUEST_INTR_SSP_TABLE, vmcs12->guest_ssp_tbl);
+	}
 }
 
 /*
@@ -2556,6 +2563,15 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	if (kvm_mpx_supported() && (!vmx->nested.nested_run_pending ||
 	    !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS)))
 		vmcs_write64(GUEST_BNDCFGS, vmx->nested.vmcs01_guest_bndcfgs);
+
+	if (kvm_cet_supported() && (!vmx->nested.nested_run_pending ||
+	    !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE))) {
+		vmcs_writel(GUEST_SSP, vmx->nested.vmcs01_guest_ssp);
+		vmcs_writel(GUEST_S_CET, vmx->nested.vmcs01_guest_s_cet);
+		vmcs_writel(GUEST_INTR_SSP_TABLE,
+			    vmx->nested.vmcs01_guest_ssp_tbl);
+	}
+
 	vmx_set_rflags(vcpu, vmcs12->guest_rflags);
 
 	/* EXCEPTION_BITMAP and CR0_GUEST_HOST_MASK should basically be the
@@ -3375,6 +3391,11 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
 	if (kvm_mpx_supported() &&
 		!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS))
 		vmx->nested.vmcs01_guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS);
+	if (kvm_cet_supported() && !vmx->nested.nested_run_pending) {
+		vmx->nested.vmcs01_guest_ssp = vmcs_readl(GUEST_SSP);
+		vmx->nested.vmcs01_guest_s_cet = vmcs_readl(GUEST_S_CET);
+		vmx->nested.vmcs01_guest_ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
+	}
 
 	/*
 	 * Overwrite vmcs01.GUEST_CR3 with L1's CR3 if EPT is disabled *and*
@@ -4001,6 +4022,9 @@ static bool is_vmcs12_ext_field(unsigned long field)
 	case GUEST_IDTR_BASE:
 	case GUEST_PENDING_DBG_EXCEPTIONS:
 	case GUEST_BNDCFGS:
+	case GUEST_SSP:
+	case GUEST_INTR_SSP_TABLE:
+	case GUEST_S_CET:
 		return true;
 	default:
 		break;
@@ -4052,6 +4076,12 @@ static void sync_vmcs02_to_vmcs12_rare(struct kvm_vcpu *vcpu,
 		vmcs_readl(GUEST_PENDING_DBG_EXCEPTIONS);
 	if (kvm_mpx_supported())
 		vmcs12->guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS);
+	if (kvm_cet_supported() && (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
+	    guest_cpuid_has(vcpu, X86_FEATURE_IBT))) {
+		vmcs12->guest_ssp = vmcs_readl(GUEST_SSP);
+		vmcs12->guest_s_cet = vmcs_readl(GUEST_S_CET);
+		vmcs12->guest_ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
+	}
 
 	vmx->nested.need_sync_vmcs02_to_vmcs12_rare = false;
 }
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 9d3a557949ac..36dc4fdb0909 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -155,6 +155,9 @@ struct nested_vmx {
 	/* to migrate it to L2 if VM_ENTRY_LOAD_DEBUG_CONTROLS is off */
 	u64 vmcs01_debugctl;
 	u64 vmcs01_guest_bndcfgs;
+	u64 vmcs01_guest_ssp;
+	u64 vmcs01_guest_s_cet;
+	u64 vmcs01_guest_ssp_tbl;
 
 	/* to migrate it to L1 if L2 writes to L1's CR8 directly */
 	int l1_tpr_threshold;
-- 
2.26.2

Re: [PATCH v5 1/3] KVM: nVMX: Sync L2 guest CET states between L1/L2

[Sean Christopherson]

On Fri, Apr 09, 2021, Yang Weijiang wrote:
> These fields are rarely updated by L1 QEMU/KVM, sync them when L1 is trying to
> read/write them and after they're changed. If CET guest entry-load bit is not
> set by L1 guest, migrate them to L2 manaully.
> 
> Opportunistically remove one blank line in previous patch.
> 
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> ---
>  arch/x86/kvm/cpuid.c      |  1 -
>  arch/x86/kvm/vmx/nested.c | 30 ++++++++++++++++++++++++++++++
>  arch/x86/kvm/vmx/vmx.h    |  3 +++
>  3 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index d191de769093..8692f53b8cd0 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -143,7 +143,6 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
>  		}
>  		vcpu->arch.guest_supported_xss =
>  			(((u64)best->edx << 32) | best->ecx) & supported_xss;
> -
>  	} else {
>  		vcpu->arch.guest_supported_xss = 0;
>  	}
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 9728efd529a1..87beb1c034e1 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -2516,6 +2516,13 @@ static void prepare_vmcs02_rare(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
>  	vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_autoload.guest.nr);
>  
>  	set_cr4_guest_host_mask(vmx);
> +
> +	if (kvm_cet_supported() && vmx->nested.nested_run_pending &&
> +	    (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE)) {
> +		vmcs_writel(GUEST_SSP, vmcs12->guest_ssp);
> +		vmcs_writel(GUEST_S_CET, vmcs12->guest_s_cet);
> +		vmcs_writel(GUEST_INTR_SSP_TABLE, vmcs12->guest_ssp_tbl);
> +	}
>  }
>  
>  /*
> @@ -2556,6 +2563,15 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>  	if (kvm_mpx_supported() && (!vmx->nested.nested_run_pending ||
>  	    !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS)))
>  		vmcs_write64(GUEST_BNDCFGS, vmx->nested.vmcs01_guest_bndcfgs);
> +
> +	if (kvm_cet_supported() && (!vmx->nested.nested_run_pending ||
> +	    !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE))) {
> +		vmcs_writel(GUEST_SSP, vmx->nested.vmcs01_guest_ssp);
> +		vmcs_writel(GUEST_S_CET, vmx->nested.vmcs01_guest_s_cet);
> +		vmcs_writel(GUEST_INTR_SSP_TABLE,
> +			    vmx->nested.vmcs01_guest_ssp_tbl);
> +	}
> +
>  	vmx_set_rflags(vcpu, vmcs12->guest_rflags);
>  
>  	/* EXCEPTION_BITMAP and CR0_GUEST_HOST_MASK should basically be the
> @@ -3375,6 +3391,11 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
>  	if (kvm_mpx_supported() &&
>  		!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS))
>  		vmx->nested.vmcs01_guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS);
> +	if (kvm_cet_supported() && !vmx->nested.nested_run_pending) {

This needs to be:

	if (kvm_cet_supported() && (!vmx->nested.nested_run_pending ||
	    !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE)))

otherwise the vmcs01_* members will be stale when emulating VM-Enter with
vcmc12.vm_entry_controls.LOAD_CET_STATE=0.

> +		vmx->nested.vmcs01_guest_ssp = vmcs_readl(GUEST_SSP);
> +		vmx->nested.vmcs01_guest_s_cet = vmcs_readl(GUEST_S_CET);
> +		vmx->nested.vmcs01_guest_ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
> +	}

Re: [PATCH v5 1/3] KVM: nVMX: Sync L2 guest CET states between L1/L2

[Yang Weijiang]

On Tue, Apr 20, 2021 at 05:35:01PM +0000, Sean Christopherson wrote:
> On Fri, Apr 09, 2021, Yang Weijiang wrote:
> > These fields are rarely updated by L1 QEMU/KVM, sync them when L1 is trying to
> > read/write them and after they're changed. If CET guest entry-load bit is not
> > set by L1 guest, migrate them to L2 manaully.
> > 
> > Opportunistically remove one blank line in previous patch.
> > 
> > Suggested-by: Sean Christopherson <seanjc@google.com>
> > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> > ---
> >  arch/x86/kvm/cpuid.c      |  1 -
> >  arch/x86/kvm/vmx/nested.c | 30 ++++++++++++++++++++++++++++++
> >  arch/x86/kvm/vmx/vmx.h    |  3 +++
> >  3 files changed, 33 insertions(+), 1 deletion(-)
> > 
> >  	vmx_set_rflags(vcpu, vmcs12->guest_rflags);
> >  
> >  	/* EXCEPTION_BITMAP and CR0_GUEST_HOST_MASK should basically be the
> > @@ -3375,6 +3391,11 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
> >  	if (kvm_mpx_supported() &&
> >  		!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS))
> >  		vmx->nested.vmcs01_guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS);
> > +	if (kvm_cet_supported() && !vmx->nested.nested_run_pending) {
> 
> This needs to be:
> 
> 	if (kvm_cet_supported() && (!vmx->nested.nested_run_pending ||
> 	    !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE)))
> 
> otherwise the vmcs01_* members will be stale when emulating VM-Enter with
> vcmc12.vm_entry_controls.LOAD_CET_STATE=0.
> 
Thanks Sean! Change is included in v6 patch series.

> > +		vmx->nested.vmcs01_guest_ssp = vmcs_readl(GUEST_SSP);
> > +		vmx->nested.vmcs01_guest_s_cet = vmcs_readl(GUEST_S_CET);
> > +		vmx->nested.vmcs01_guest_ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
> > +	}

[PATCH v5 2/3] KVM: nVMX: Set X86_CR4_CET in cr4_fixed1_bits if CET IBT is enabled

[Yang Weijiang]

CET SHSTK and IBT are independently controlled by kernel, set X86_CR4_CET
bit in cr4_fixed1_bits if either of them is enabled so that nested guest
can enjoy the feature.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
 arch/x86/kvm/vmx/vmx.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e78650bf8ae8..bd89b5a24c38 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7267,6 +7267,7 @@ static void nested_vmx_cr_fixed1_bits_update(struct kvm_vcpu *vcpu)
 	cr4_fixed1_update(X86_CR4_UMIP,       ecx, feature_bit(UMIP));
 	cr4_fixed1_update(X86_CR4_LA57,       ecx, feature_bit(LA57));
 	cr4_fixed1_update(X86_CR4_CET,	      ecx, feature_bit(SHSTK));
+	cr4_fixed1_update(X86_CR4_CET,	      edx, feature_bit(IBT));
 
 #undef cr4_fixed1_update
 }
-- 
2.26.2

[PATCH v5 3/3] KVM: nVMX: Add CET entry/exit load bits to evmcs unsupported list

[Yang Weijiang]

Nested guest doesn't support CET when KVM is running as an intermediate
layer between two Hyper-Vs for now, so mask out related CET entry/exit
load bits. Relevant enabling patches will be posted as a separate patch
series.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Suggested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
 arch/x86/kvm/vmx/evmcs.c | 4 ++--
 arch/x86/kvm/vmx/evmcs.h | 6 ++++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
index 41f24661af04..9f81db51fd8b 100644
--- a/arch/x86/kvm/vmx/evmcs.c
+++ b/arch/x86/kvm/vmx/evmcs.c
@@ -351,11 +351,11 @@ void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata)
 	switch (msr_index) {
 	case MSR_IA32_VMX_EXIT_CTLS:
 	case MSR_IA32_VMX_TRUE_EXIT_CTLS:
-		ctl_high &= ~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
+		ctl_high &= ~EVMCS1_UNSUPPORTED_VMEXIT_CTRL;
 		break;
 	case MSR_IA32_VMX_ENTRY_CTLS:
 	case MSR_IA32_VMX_TRUE_ENTRY_CTLS:
-		ctl_high &= ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
+		ctl_high &= ~EVMCS1_UNSUPPORTED_VMENTRY_CTRL;
 		break;
 	case MSR_IA32_VMX_PROCBASED_CTLS2:
 		ctl_high &= ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h
index bd41d9462355..25588694eb04 100644
--- a/arch/x86/kvm/vmx/evmcs.h
+++ b/arch/x86/kvm/vmx/evmcs.h
@@ -59,8 +59,10 @@ DECLARE_STATIC_KEY_FALSE(enable_evmcs);
 	 SECONDARY_EXEC_SHADOW_VMCS |					\
 	 SECONDARY_EXEC_TSC_SCALING |					\
 	 SECONDARY_EXEC_PAUSE_LOOP_EXITING)
-#define EVMCS1_UNSUPPORTED_VMEXIT_CTRL (VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL)
-#define EVMCS1_UNSUPPORTED_VMENTRY_CTRL (VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL)
+#define EVMCS1_UNSUPPORTED_VMEXIT_CTRL (VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL | \
+					VM_EXIT_LOAD_CET_STATE)
+#define EVMCS1_UNSUPPORTED_VMENTRY_CTRL (VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL | \
+					 VM_ENTRY_LOAD_CET_STATE)
 #define EVMCS1_UNSUPPORTED_VMFUNC (VMX_VMFUNC_EPTP_SWITCHING)
 
 #if IS_ENABLED(CONFIG_HYPERV)
-- 
2.26.2