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Date: Tue, 2 Apr 2019 13:21:47 -0700
From: Sean Christopherson <sean.j.christopherson@...el.com>
To: Yang Weijiang <weijiang.yang@...el.com>
Cc: pbonzini@...hat.com, kvm@...r.kernel.org, mst@...hat.com,
rkrcmar@...hat.com, jmattson@...gle.com,
linux-kernel@...r.kernel.org, yu-cheng.yu@...el.com,
Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Subject: Re: [RFC PATCH v4 2/8] KVM:CPUID: Add CET CPUID support for Guest
On Mon, Mar 18, 2019 at 11:03:45PM +0800, Yang Weijiang wrote:
> CET SHSTK and IBT capability are reported via
> CPUID.(EAX=7, ECX=0):ECX[bit 7] and EDX[bit 20] respectively.
> CR4.CET[bit 23] is CET master enable bit, it controls CET feature
> enabling. CET user mode and supervisor mode xsaves component size
> is reported via CPUID.(EAX=0xD, ECX=1):ECX[bit 11] and ECX[bit 12]
> respectively.
>
> Note: Although SHSTK or IBT can be enabled independently,
> both of them are controlled by CR4.CET.
>
> Signed-off-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
> ---
> arch/x86/include/asm/kvm_host.h | 4 +++-
> arch/x86/kvm/cpuid.c | 41 ++++++++++++++++++++++-----------
> arch/x86/kvm/vmx.c | 6 +++++
> arch/x86/kvm/x86.h | 4 ++++
> 4 files changed, 40 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 55e51ff7e421..fc038bf1924a 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -90,7 +90,8 @@
> | 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)
>
> @@ -1185,6 +1186,7 @@ struct kvm_x86_ops {
>
> int (*nested_enable_evmcs)(struct kvm_vcpu *vcpu,
> uint16_t *vmcs_version);
> + u64 (*vmx_supported_xss)(void);
> };
>
> struct kvm_arch_async_pf {
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 7bcfa61375c0..53abd6019c68 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->vmx_supported_xss();
> +}
> +
> #define F(x) bit(X86_FEATURE_##x)
>
> /* For scattered features from cpufeatures.h; we currently expose none */
> @@ -406,12 +411,12 @@ 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(CLDEMOTE) | 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(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(IBT);
The features should not be advertised to userspace until KVM fully supports
them, which AIUI doesn't happen until the last patch in this series.
>
> /* all calls to cpuid_count() should be made on the same cpu */
> get_cpu();
> @@ -564,14 +569,16 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> }
> case 0xd: {
> int idx, i;
> - u64 supported = kvm_supported_xcr0();
> + u64 u_supported = kvm_supported_xcr0();
> + u64 s_supported = kvm_supported_xss();
> + u64 supported;
>
> - 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) {
> @@ -583,19 +590,25 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> if (idx == 1) {
> entry[i].eax &= kvm_cpuid_D_1_eax_x86_features;
> cpuid_mask(&entry[i].eax, CPUID_D_1_EAX);
> + supported = u_supported | s_supported;
> entry[i].ebx = 0;
> - if (entry[i].eax & (F(XSAVES)|F(XSAVEC)))
> + entry[i].edx = 0;
> + entry[i].ecx &= s_supported;
> + if (entry[i].eax & (F(XSAVES) | F(XSAVEC))) {
> entry[i].ebx =
> - xstate_required_size(supported,
> - true);
> + xstate_required_size(supported,
> + true);
The indentation depth is getting pretty gnarly, I at a glance I think it'd
be much cleaner to move the guts of the for loop to a helper, e.g.:
for (idx = 1, i = 1; idx < 64; ++idx, ++i) {
if (*nent >= maxnent)
goto out;
__do_cpuid_0xd_ent(i, u_supported, s_supported);
++*nent;
}
> + }
> } else {
> + supported = (entry[i].ecx & 1) ? s_supported :
> + u_supported;
> if (entry[i].eax == 0 || !(supported & mask))
> continue;
> - if (WARN_ON_ONCE(entry[i].ecx & 1))
> - continue;
> + entry[i].ecx &= 1;
> + entry[i].edx = 0;
> + if (entry[i].ecx)
> + entry[i].ebx = 0;
> }
> - entry[i].ecx = 0;
> - entry[i].edx = 0;
> entry[i].flags |=
> KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> ++*nent;
Not your code, but the "++i;" that's sitting below this should be handled
in the for loop (see above). This is a good opportunity to make that change.
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 7bbb8b26e901..53cef5a3db96 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -4169,6 +4169,11 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> return 0;
> }
>
> +static __always_inline u64 vmx_supported_xss(void)
> +{
> + return host_xss;
> +}
> +
> static void vmx_leave_nested(struct kvm_vcpu *vcpu);
>
> /*
> @@ -15107,6 +15112,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> .enable_smi_window = enable_smi_window,
>
> .nested_enable_evmcs = nested_enable_evmcs,
> + .vmx_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 224cd0a47568..c61da41c3c5c 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -283,6 +283,10 @@ 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_SHSTK_USER \
> + | XFEATURE_MASK_SHSTK_KERNEL)
> +
> extern u64 host_xcr0;
>
> extern u64 kvm_supported_xcr0(void);
> --
> 2.17.1
>
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