diff mbox series

[RESEND,v13,11/11] KVM: x86: Enable CET virtualization and advertise CET to userspace

Message ID 20200716031627.11492-12-weijiang.yang@intel.com (mailing list archive)
State New, archived
Headers show
Series Introduce support for guest CET feature | expand

Commit Message

Yang, Weijiang July 16, 2020, 3:16 a.m. UTC 
Set the feature bits so that CET capabilities can be seen in guest via
CPUID enumeration. Add CR4.CET bit support in order to allow guest set CET
master control bit(CR4.CET).

Disable KVM CET feature once unrestricted_guest is turned off because
KVM cannot emulate guest CET behavior well in this case.

Don't expose CET feature if dependent CET bits are cleared in host XSS.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
 arch/x86/include/asm/kvm_host.h |  3 ++-
 arch/x86/kvm/cpuid.c            |  5 +++--
 arch/x86/kvm/vmx/vmx.c          |  5 +++++
 arch/x86/kvm/x86.c              | 11 +++++++++++
 4 files changed, 21 insertions(+), 3 deletions(-)

Comments

Sean Christopherson July 22, 2020, 9:33 p.m. UTC | #1 
On Thu, Jul 16, 2020 at 11:16:27AM +0800, Yang Weijiang wrote:
> Set the feature bits so that CET capabilities can be seen in guest via
> CPUID enumeration. Add CR4.CET bit support in order to allow guest set CET
> master control bit(CR4.CET).
> 
> Disable KVM CET feature once unrestricted_guest is turned off because
> KVM cannot emulate guest CET behavior well in this case.
> 
> Don't expose CET feature if dependent CET bits are cleared in host XSS.
> 
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  3 ++-
>  arch/x86/kvm/cpuid.c            |  5 +++--
>  arch/x86/kvm/vmx/vmx.c          |  5 +++++
>  arch/x86/kvm/x86.c              | 11 +++++++++++
>  4 files changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e8c749596ba2..c4c82db68b6a 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -99,7 +99,8 @@
>  			  | X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR | X86_CR4_PCIDE \
>  			  | X86_CR4_OSXSAVE | X86_CR4_SMEP | X86_CR4_FSGSBASE \
>  			  | X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_VMXE \
> -			  | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP))
> +			  | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP \
> +			  | X86_CR4_CET))
>  
>  #define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)
>  
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index d97b2a6e8a8c..a085b8c57f34 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -340,7 +340,8 @@ void kvm_set_cpu_caps(void)
>  		F(AVX512VBMI) | F(LA57) | F(PKU) | 0 /*OSPKE*/ | F(RDPID) |
>  		F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |
>  		F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |
> -		F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/
> +		F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/ |
> +		F(SHSTK)
>  	);
>  	/* Set LA57 based on hardware capability. */
>  	if (cpuid_ecx(7) & F(LA57))
> @@ -356,7 +357,7 @@ void kvm_set_cpu_caps(void)
>  	kvm_cpu_cap_mask(CPUID_7_EDX,
>  		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
>  		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
> -		F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM)
> +		F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) | F(IBT)
>  	);
>  
>  	/* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 5d4250b9dec8..31593339b6fe 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7542,6 +7542,11 @@ static __init void vmx_set_cpu_caps(void)
>  
>  	if (vmx_waitpkg_supported())
>  		kvm_cpu_cap_check_and_set(X86_FEATURE_WAITPKG);
> +
> +	if (!enable_unrestricted_guest) {

This also needs to check cpu_has_load_cet_ctrl().

> +		kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
> +		kvm_cpu_cap_clear(X86_FEATURE_IBT);
> +	}
>  }
>  
>  static void vmx_request_immediate_exit(struct kvm_vcpu *vcpu)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 76892fb0b0a0..c7393d62ad72 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9808,10 +9808,21 @@ int kvm_arch_hardware_setup(void *opaque)
>  	if (kvm_cpu_cap_has(X86_FEATURE_XSAVES))
>  		supported_xss = host_xss & KVM_SUPPORTED_XSS;
>  
> +	if (!(supported_xss & (XFEATURE_MASK_CET_USER |
> +	    XFEATURE_MASK_CET_KERNEL))) {
> +		kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
> +		kvm_cpu_cap_clear(X86_FEATURE_IBT);

I played around with a variety of options, and ended up with:

	if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
		supported_xss = 0;
	else
		supported_xss &= host_xss;

	/* Update CET features now that supported_xss is finalized. */
	if (!kvm_cet_supported()) {
		kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
		kvm_cpu_cap_clear(X86_FEATURE_IBT);
	}

in x86.c / kvm_arch_hardware_setup(), and 

	if (!cpu_has_load_cet_ctrl() || !enable_unrestricted_guest) {
		kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
		kvm_cpu_cap_clear(X86_FEATURE_IBT);
	} else if (kvm_cpu_cap_has(X86_FEATURE_SHSTK) ||
		   kvm_cpu_cap_has(X86_FEATURE_IBT)) {
		supported_xss |= XFEATURE_MASK_CET_USER |
				 XFEATURE_MASK_CET_KERNEL;
	}

in vmx.c / vmx_set_cpu_caps.

That avoids KVM_SUPPORTED_XSS, and was the least ugly option I could devise
for avoiding the cyclical dependency between XSS and SHSTK/IBT without
potentially exploding SVM in the future.

> +	}
> +
>  #define __kvm_cpu_cap_has(UNUSED_, f) kvm_cpu_cap_has(f)
>  	cr4_reserved_bits = __cr4_reserved_bits(__kvm_cpu_cap_has, UNUSED_);
>  #undef __kvm_cpu_cap_has
>  
> +	if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK) &&
> +	    !kvm_cpu_cap_has(X86_FEATURE_IBT))
> +		supported_xss &= ~(XFEATURE_MASK_CET_USER |
> +				   XFEATURE_MASK_CET_KERNEL);
> +
>  	if (kvm_has_tsc_control) {
>  		/*
>  		 * Make sure the user can only configure tsc_khz values that
> -- 
> 2.17.2
>
diff mbox series

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e8c749596ba2..c4c82db68b6a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -99,7 +99,8 @@ 
 			  | X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR | X86_CR4_PCIDE \
 			  | X86_CR4_OSXSAVE | X86_CR4_SMEP | X86_CR4_FSGSBASE \
 			  | X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_VMXE \
-			  | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP))
+			  | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP \
+			  | X86_CR4_CET))
 
 #define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)
 
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index d97b2a6e8a8c..a085b8c57f34 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -340,7 +340,8 @@  void kvm_set_cpu_caps(void)
 		F(AVX512VBMI) | F(LA57) | F(PKU) | 0 /*OSPKE*/ | F(RDPID) |
 		F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |
 		F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |
-		F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/
+		F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/ |
+		F(SHSTK)
 	);
 	/* Set LA57 based on hardware capability. */
 	if (cpuid_ecx(7) & F(LA57))
@@ -356,7 +357,7 @@  void kvm_set_cpu_caps(void)
 	kvm_cpu_cap_mask(CPUID_7_EDX,
 		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
 		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
-		F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM)
+		F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) | F(IBT)
 	);
 
 	/* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 5d4250b9dec8..31593339b6fe 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7542,6 +7542,11 @@  static __init void vmx_set_cpu_caps(void)
 
 	if (vmx_waitpkg_supported())
 		kvm_cpu_cap_check_and_set(X86_FEATURE_WAITPKG);
+
+	if (!enable_unrestricted_guest) {
+		kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
+		kvm_cpu_cap_clear(X86_FEATURE_IBT);
+	}
 }
 
 static void vmx_request_immediate_exit(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 76892fb0b0a0..c7393d62ad72 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9808,10 +9808,21 @@  int kvm_arch_hardware_setup(void *opaque)
 	if (kvm_cpu_cap_has(X86_FEATURE_XSAVES))
 		supported_xss = host_xss & KVM_SUPPORTED_XSS;
 
+	if (!(supported_xss & (XFEATURE_MASK_CET_USER |
+	    XFEATURE_MASK_CET_KERNEL))) {
+		kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
+		kvm_cpu_cap_clear(X86_FEATURE_IBT);
+	}
+
 #define __kvm_cpu_cap_has(UNUSED_, f) kvm_cpu_cap_has(f)
 	cr4_reserved_bits = __cr4_reserved_bits(__kvm_cpu_cap_has, UNUSED_);
 #undef __kvm_cpu_cap_has
 
+	if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK) &&
+	    !kvm_cpu_cap_has(X86_FEATURE_IBT))
+		supported_xss &= ~(XFEATURE_MASK_CET_USER |
+				   XFEATURE_MASK_CET_KERNEL);
+
 	if (kvm_has_tsc_control) {
 		/*
 		 * Make sure the user can only configure tsc_khz values that