Re: [PATCH v7 20/26] x86/cpufeature: Add User-Mode Instruction Prevention definitions

[Paolo Bonzini]

On 05/05/2017 20:17, Ricardo Neri wrote:
> User-Mode Instruction Prevention is a security feature present in new
> Intel processors that, when set, prevents the execution of a subset of
> instructions if such instructions are executed in user mode (CPL > 0).
> Attempting to execute such instructions causes a general protection
> exception.
> 
> The subset of instructions comprises:
> 
>  * SGDT - Store Global Descriptor Table
>  * SIDT - Store Interrupt Descriptor Table
>  * SLDT - Store Local Descriptor Table
>  * SMSW - Store Machine Status Word
>  * STR  - Store Task Register
> 
> This feature is also added to the list of disabled-features to allow
> a cleaner handling of build-time configuration.
> 
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: H. Peter Anvin <hpa@xxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Brian Gerst <brgerst@xxxxxxxxx>
> Cc: Chen Yucong <slaoub@xxxxxxxxx>
> Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> Cc: Huang Rui <ray.huang@xxxxxxx>
> Cc: Jiri Slaby <jslaby@xxxxxxx>
> Cc: Jonathan Corbet <corbet@xxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Ravi V. Shankar <ravi.v.shankar@xxxxxxxxx>
> Cc: Shuah Khan <shuah@xxxxxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Tony Luck <tony.luck@xxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Liang Z. Li <liang.z.li@xxxxxxxxx>
> Cc: Alexandre Julliard <julliard@xxxxxxxxxx>
> Cc: Stas Sergeev <stsp@xxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: linux-msdos@xxxxxxxxxxxxxxx
> 
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>

Would it be possible to have this patch in a topic branch for KVM's
consumption?

Thanks,

Paolo

> ---
>  arch/x86/include/asm/cpufeatures.h          | 1 +
>  arch/x86/include/asm/disabled-features.h    | 8 +++++++-
>  arch/x86/include/uapi/asm/processor-flags.h | 2 ++
>  3 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 2701e5f..f1d61d2 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -289,6 +289,7 @@
>  
>  /* Intel-defined CPU features, CPUID level 0x00000007:0 (ecx), word 16 */
>  #define X86_FEATURE_AVX512VBMI  (16*32+ 1) /* AVX512 Vector Bit Manipulation instructions*/
> +#define X86_FEATURE_UMIP	(16*32+ 2) /* User Mode Instruction Protection */
>  #define X86_FEATURE_PKU		(16*32+ 3) /* Protection Keys for Userspace */
>  #define X86_FEATURE_OSPKE	(16*32+ 4) /* OS Protection Keys Enable */
>  #define X86_FEATURE_AVX512_VPOPCNTDQ (16*32+14) /* POPCNT for vectors of DW/QW */
> diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
> index 5dff775..7adaef7 100644
> --- a/arch/x86/include/asm/disabled-features.h
> +++ b/arch/x86/include/asm/disabled-features.h
> @@ -16,6 +16,12 @@
>  # define DISABLE_MPX	(1<<(X86_FEATURE_MPX & 31))
>  #endif
>  
> +#ifdef CONFIG_X86_INTEL_UMIP
> +# define DISABLE_UMIP	0
> +#else
> +# define DISABLE_UMIP	(1<<(X86_FEATURE_UMIP & 31))
> +#endif
> +
>  #ifdef CONFIG_X86_64
>  # define DISABLE_VME		(1<<(X86_FEATURE_VME & 31))
>  # define DISABLE_K6_MTRR	(1<<(X86_FEATURE_K6_MTRR & 31))
> @@ -61,7 +67,7 @@
>  #define DISABLED_MASK13	0
>  #define DISABLED_MASK14	0
>  #define DISABLED_MASK15	0
> -#define DISABLED_MASK16	(DISABLE_PKU|DISABLE_OSPKE|DISABLE_LA57)
> +#define DISABLED_MASK16	(DISABLE_PKU|DISABLE_OSPKE|DISABLE_LA57|DISABLE_UMIP)
>  #define DISABLED_MASK17	0
>  #define DISABLED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 18)
>  
> diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
> index 567de50..d2c2af8 100644
> --- a/arch/x86/include/uapi/asm/processor-flags.h
> +++ b/arch/x86/include/uapi/asm/processor-flags.h
> @@ -104,6 +104,8 @@
>  #define X86_CR4_OSFXSR		_BITUL(X86_CR4_OSFXSR_BIT)
>  #define X86_CR4_OSXMMEXCPT_BIT	10 /* enable unmasked SSE exceptions */
>  #define X86_CR4_OSXMMEXCPT	_BITUL(X86_CR4_OSXMMEXCPT_BIT)
> +#define X86_CR4_UMIP_BIT	11 /* enable UMIP support */
> +#define X86_CR4_UMIP		_BITUL(X86_CR4_UMIP_BIT)
>  #define X86_CR4_VMXE_BIT	13 /* enable VMX virtualization */
>  #define X86_CR4_VMXE		_BITUL(X86_CR4_VMXE_BIT)
>  #define X86_CR4_SMXE_BIT	14 /* enable safer mode (TXT) */
>