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Date:   Wed, 5 Jun 2019 10:51:51 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Yang Weijiang <weijiang.yang@...el.com>, pbonzini@...hat.com,
        mst@...hat.com, rkrcmar@...hat.com, jmattson@...gle.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        yu-cheng.yu@...el.com
Subject: Re: [PATCH v5 2/8] KVM: x86: Implement CET CPUID support for Guest

On Tue, Jun 04, 2019 at 12:58:01PM -0700, Sean Christopherson wrote:
> On Wed, May 22, 2019 at 03:00:55PM +0800, Yang Weijiang wrote:
> > CET SHSTK and IBT features are introduced here so that
> > CPUID.(EAX=7, ECX=0):ECX[bit 7] and EDX[bit 20] reflect them.
> > CET xsave components for supervisor and user mode are reported
> > via CPUID.(EAX=0xD, ECX=1):ECX[bit 11] and ECX[bit 12]
> > respectively.
> > 
> > To make the code look clean, wrap CPUID(0xD,n>=1) report code in
> > a helper function now.
> 
> Create the helper in a separate patch so that it's introduced without
> any functional changes.
OK, will add a new patch to put the helper.
>  
> > Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
> > Co-developed-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h |  4 +-
> >  arch/x86/kvm/cpuid.c            | 97 +++++++++++++++++++++------------
> >  arch/x86/kvm/vmx/vmx.c          |  6 ++
> >  arch/x86/kvm/x86.h              |  4 ++
> >  4 files changed, 76 insertions(+), 35 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index a5db4475e72d..8c3f0ddc7676 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -91,7 +91,8 @@
> >  			  | 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))
> 
> As I mentioned in v4, the patch ordering is wrong.  Features shouldn't be
> advertised to userspace or exposed to the guest until they're fully
> supported in KVM, i.e. the bulk of this patch to advertise the CPUID bits
> and allow CR4.CET=1 belongs at the end of the series.
> 
How about merge it to patch 6/8?
> >  #define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)
> >  
> > @@ -1192,6 +1193,7 @@ struct kvm_x86_ops {
> >  	int (*nested_enable_evmcs)(struct kvm_vcpu *vcpu,
> >  				   uint16_t *vmcs_version);
> >  	uint16_t (*nested_get_evmcs_version)(struct kvm_vcpu *vcpu);
> > +	u64 (*supported_xss)(void);
> >  };
> >  
> >  struct kvm_arch_async_pf {
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index fd3951638ae4..b9fc967fe55a 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -65,6 +65,11 @@ u64 kvm_supported_xcr0(void)
> >  	return xcr0;
> >  }
> >  
> > +u64 kvm_supported_xss(void)
> > +{
> > +	return KVM_SUPPORTED_XSS & kvm_x86_ops->supported_xss();
> > +}
> > +
> >  #define F(x) bit(X86_FEATURE_##x)
> >  
> >  int kvm_update_cpuid(struct kvm_vcpu *vcpu)
> > @@ -316,6 +321,50 @@ static int __do_cpuid_ent_emulated(struct kvm_cpuid_entry2 *entry,
> >  	return 0;
> >  }
> >  
> > +static inline int __do_cpuid_dx_leaf(struct kvm_cpuid_entry2 *entry, int *nent,
> > +				     int maxnent, u64 xss_mask, u64 xcr0_mask,
> > +				     u32 eax_mask)
> > +{
> > +	int idx, i;
> > +	u64 mask;
> > +	u64 supported;
> > +
> > +	for (idx = 1, i = 1; idx < 64; ++idx) {
> > +		mask = ((u64)1 << idx);
> > +		if (*nent >= maxnent)
> > +			return -EINVAL;
> > +
> > +		do_cpuid_1_ent(&entry[i], 0xD, idx);
> > +		if (idx == 1) {
> > +			entry[i].eax &= eax_mask;
> > +			cpuid_mask(&entry[i].eax, CPUID_D_1_EAX);
> > +			supported = xcr0_mask | xss_mask;
> > +			entry[i].ebx = 0;
> > +			entry[i].edx = 0;
> > +			entry[i].ecx &= xss_mask;
> > +			if (entry[i].eax & (F(XSAVES) | F(XSAVEC))) {
> > +				entry[i].ebx =
> > +					xstate_required_size(supported,
> > +							     true);
> > +			}
> > +		} else {
> > +			supported = (entry[i].ecx & 1) ? xss_mask :
> > +				     xcr0_mask;
> > +			if (entry[i].eax == 0 || !(supported & mask))
> > +				continue;
> > +			entry[i].ecx &= 1;
> > +			entry[i].edx = 0;
> > +			if (entry[i].ecx)
> > +				entry[i].ebx = 0;
> > +		}
> > +		entry[i].flags |=
> > +			KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> > +		++*nent;
> > +		++i;
> > +	}
> > +	return 0;
> > +}
> > +
> >  static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> >  				 u32 index, int *nent, int maxnent)
> >  {
> > @@ -405,12 +454,13 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> >  		F(AVX512VBMI) | F(LA57) | F(PKU) | 0 /*OSPKE*/ |
> >  		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);
> > +		F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | F(SHSTK);
> >  
> >  	/* cpuid 7.0.edx*/
> >  	const u32 kvm_cpuid_7_0_edx_x86_features =
> >  		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
> > -		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP);
> > +		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
> > +		F(IBT);
> >  
> >  	/* all calls to cpuid_count() should be made on the same cpu */
> >  	get_cpu();
> > @@ -565,44 +615,23 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> >  		break;
> >  	}
> >  	case 0xd: {
> > -		int idx, i;
> > -		u64 supported = kvm_supported_xcr0();
> > +		u64 u_supported = kvm_supported_xcr0();
> > +		u64 s_supported = kvm_supported_xss();
> > +		u32 eax_mask = kvm_cpuid_D_1_eax_x86_features;
> >  
> > -		entry->eax &= supported;
> > -		entry->ebx = xstate_required_size(supported, false);
> > +		entry->eax &= u_supported;
> > +		entry->ebx = xstate_required_size(u_supported, false);
> >  		entry->ecx = entry->ebx;
> > -		entry->edx &= supported >> 32;
> > +		entry->edx &= u_supported >> 32;
> >  		entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> > -		if (!supported)
> > +
> > +		if (!u_supported && !s_supported)
> >  			break;
> >  
> > -		for (idx = 1, i = 1; idx < 64; ++idx) {
> > -			u64 mask = ((u64)1 << idx);
> > -			if (*nent >= maxnent)
> > -				goto out;
> > +		if (__do_cpuid_dx_leaf(entry, nent, maxnent, s_supported,
> > +				       u_supported, eax_mask) < 0)
> > +			goto out;
> >  
> > -			do_cpuid_1_ent(&entry[i], function, idx);
> > -			if (idx == 1) {
> > -				entry[i].eax &= kvm_cpuid_D_1_eax_x86_features;
> > -				cpuid_mask(&entry[i].eax, CPUID_D_1_EAX);
> > -				entry[i].ebx = 0;
> > -				if (entry[i].eax & (F(XSAVES)|F(XSAVEC)))
> > -					entry[i].ebx =
> > -						xstate_required_size(supported,
> > -								     true);
> > -			} else {
> > -				if (entry[i].eax == 0 || !(supported & mask))
> > -					continue;
> > -				if (WARN_ON_ONCE(entry[i].ecx & 1))
> > -					continue;
> > -			}
> > -			entry[i].ecx = 0;
> > -			entry[i].edx = 0;
> > -			entry[i].flags |=
> > -			       KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> > -			++*nent;
> > -			++i;
> > -		}
> >  		break;
> >  	}
> >  	/* Intel PT */
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index 7c015416fd58..574428375ff9 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -1637,6 +1637,11 @@ static inline bool vmx_feature_control_msr_valid(struct kvm_vcpu *vcpu,
> >  	return !(val & ~valid_bits);
> >  }
> >  
> > +static __always_inline u64 vmx_supported_xss(void)
> 
> This can't be __always_inline since it's invoked indirectly.  Out of
> curiosity, does the compiler generate a warning of any kind?
> 
So what's your suggestion? just remove it?
> > +{
> > +	return host_xss;
> > +}
> > +
> >  static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
> >  {
> >  	switch (msr->index) {
> > @@ -7711,6 +7716,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> >  	.set_nested_state = NULL,
> >  	.get_vmcs12_pages = NULL,
> >  	.nested_enable_evmcs = NULL,
> > +	.supported_xss = vmx_supported_xss,
> >  };
> >  
> >  static void vmx_cleanup_l1d_flush(void)
> > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> > index 28406aa1136d..e96616149f84 100644
> > --- a/arch/x86/kvm/x86.h
> > +++ b/arch/x86/kvm/x86.h
> > @@ -288,6 +288,10 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
> >  				| XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \
> >  				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
> >  				| XFEATURE_MASK_PKRU)
> > +
> > +#define KVM_SUPPORTED_XSS	(XFEATURE_MASK_CET_USER \
> > +				| XFEATURE_MASK_CET_KERNEL)
> > +
> >  extern u64 host_xcr0;
> >  
> >  extern u64 kvm_supported_xcr0(void);
> > -- 
> > 2.17.2
> > 

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