linux-kernel - Re: [PATCH 4/5] KVM: x86: add support for emulating UMIP

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Date:   Wed, 15 Nov 2017 08:42:02 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kvm <kvm@...r.kernel.org>, Radim Krcmar <rkrcmar@...hat.com>
Subject: Re: [PATCH 4/5] KVM: x86: add support for emulating UMIP

2017-11-13 22:40 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
> The User-Mode Instruction Prevention feature present in recent Intel
> processor prevents a group of instructions (sgdt, sidt, sldt, smsw, and
> str) from being executed with CPL > 0. Otherwise, a general protection
> fault is issued.
>
> UMIP instructions in general are also able to trigger vmexits, so we can
> actually emulate UMIP on older processors.  This commit sets up the
> infrastructure so that kvm-intel.ko and kvm-amd.ko can set the UMIP
> feature bit for CPUID even if the feature is not actually available
> in hardware.
>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Reviewed-by: Wanpeng Li <wanpeng.li@...mail.com>

> ---
>  arch/x86/include/asm/kvm_host.h | 1 +
>  arch/x86/kvm/cpuid.c            | 2 ++
>  arch/x86/kvm/svm.c              | 6 ++++++
>  arch/x86/kvm/vmx.c              | 6 ++++++
>  4 files changed, 15 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 1b005ccf4d0b..f0a4f107a97f 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1004,6 +1004,7 @@ struct kvm_x86_ops {
>         void (*handle_external_intr)(struct kvm_vcpu *vcpu);
>         bool (*mpx_supported)(void);
>         bool (*xsaves_supported)(void);
> +       bool (*umip_emulated)(void);
>
>         int (*check_nested_events)(struct kvm_vcpu *vcpu, bool external_intr);
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 77fb8732b47b..2b3b06458f6f 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -327,6 +327,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>         unsigned f_invpcid = kvm_x86_ops->invpcid_supported() ? F(INVPCID) : 0;
>         unsigned f_mpx = kvm_mpx_supported() ? F(MPX) : 0;
>         unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0;
> +       unsigned f_umip = kvm_x86_ops->umip_emulated() ? F(UMIP) : 0;
>
>         /* cpuid 1.edx */
>         const u32 kvm_cpuid_1_edx_x86_features =
> @@ -473,6 +474,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>                         entry->ebx |= F(TSC_ADJUST);
>                         entry->ecx &= kvm_cpuid_7_0_ecx_x86_features;
>                         cpuid_mask(&entry->ecx, CPUID_7_ECX);
> +                       entry->ecx |= f_umip;
>                         /* PKU is not yet implemented for shadow paging. */
>                         if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE))
>                                 entry->ecx &= ~F(PKU);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 0e68f0b3cbf7..be7fc7e5ee7e 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -5174,6 +5174,11 @@ static bool svm_xsaves_supported(void)
>         return false;
>  }
>
> +static bool svm_umip_emulated(void)
> +{
> +       return false;
> +}
> +
>  static bool svm_has_wbinvd_exit(void)
>  {
>         return true;
> @@ -5485,6 +5490,7 @@ static void svm_setup_mce(struct kvm_vcpu *vcpu)
>         .invpcid_supported = svm_invpcid_supported,
>         .mpx_supported = svm_mpx_supported,
>         .xsaves_supported = svm_xsaves_supported,
> +       .umip_emulated = svm_umip_emulated,
>
>         .set_supported_cpuid = svm_set_supported_cpuid,
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 8917e100ddeb..6c474c94e154 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -9095,6 +9095,11 @@ static bool vmx_xsaves_supported(void)
>                 SECONDARY_EXEC_XSAVES;
>  }
>
> +static bool vmx_umip_emulated(void)
> +{
> +       return false;
> +}
> +
>  static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx)
>  {
>         u32 exit_intr_info;
> @@ -12038,6 +12043,7 @@ static void vmx_setup_mce(struct kvm_vcpu *vcpu)
>         .handle_external_intr = vmx_handle_external_intr,
>         .mpx_supported = vmx_mpx_supported,
>         .xsaves_supported = vmx_xsaves_supported,
> +       .umip_emulated = vmx_umip_emulated,
>
>         .check_nested_events = vmx_check_nested_events,
>
> --
> 1.8.3.1
>
>