linux-kernel - Re: [PATCH v5 2/5] x86/cpufeatures: Add X86_FEATURE_SGX

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Message-ID: <09fbf33ae17587c204e7f436887c48367f6797f0.camel@intel.com>
Date: Mon, 19 May 2025 10:53:02 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "Reshetova, Elena" <elena.reshetova@...el.com>, "Hansen, Dave"
	<dave.hansen@...el.com>
CC: "Raynor, Scott" <scott.raynor@...el.com>, "linux-sgx@...r.kernel.org"
	<linux-sgx@...r.kernel.org>, "Scarlata, Vincent R"
	<vincent.r.scarlata@...el.com>, "x86@...nel.org" <x86@...nel.org>,
	"jarkko@...nel.org" <jarkko@...nel.org>, "Annapurve, Vishal"
	<vannapurve@...gle.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Mallick, Asit K" <asit.k.mallick@...el.com>,
	"Aktas, Erdem" <erdemaktas@...gle.com>, "Cai, Chong" <chongc@...gle.com>,
	"bondarn@...gle.com" <bondarn@...gle.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "dionnaglaze@...gle.com" <dionnaglaze@...gle.com>
Subject: Re: [PATCH v5 2/5] x86/cpufeatures: Add X86_FEATURE_SGX_EUPDATESVN
 feature flag

On Mon, 2025-05-19 at 10:24 +0300, Elena Reshetova wrote:
> Add a flag indicating whenever ENCLS[EUPDATESVN] SGX instruction
> is supported. This will be used by SGX driver to perform CPU
> SVN updates.
> 
> Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
> ---
>  arch/x86/include/asm/cpufeatures.h       | 1 +
>  arch/x86/kernel/cpu/scattered.c          | 1 +
>  tools/arch/x86/include/asm/cpufeatures.h | 1 +
>  3 files changed, 3 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 6c2c152d8a67..ed0c0fa5822a 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -481,6 +481,7 @@
>  #define X86_FEATURE_AMD_HETEROGENEOUS_CORES (21*32 + 6) /* Heterogeneous Core Topology */
>  #define X86_FEATURE_AMD_WORKLOAD_CLASS	(21*32 + 7) /* Workload Classification */
>  #define X86_FEATURE_PREFER_YMM		(21*32 + 8) /* Avoid ZMM registers due to downclocking */
> +#define X86_FEATURE_SGX_EUPDATESVN	(21*32 + 9) /* Support for ENCLS[EUPDATESVN] instruction */
>  
>  /*
>   * BUG word(s)
> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
> index 16f3ca30626a..a7e1fcedca3c 100644
> --- a/arch/x86/kernel/cpu/scattered.c
> +++ b/arch/x86/kernel/cpu/scattered.c
> @@ -41,6 +41,7 @@ static const struct cpuid_bit cpuid_bits[] = {
>  	{ X86_FEATURE_PER_THREAD_MBA,		CPUID_ECX,  0, 0x00000010, 3 },
>  	{ X86_FEATURE_SGX1,			CPUID_EAX,  0, 0x00000012, 0 },
>  	{ X86_FEATURE_SGX2,			CPUID_EAX,  1, 0x00000012, 0 },
> +	{ X86_FEATURE_SGX_EUPDATESVN,	CPUID_EAX, 10, 0x00000012, 0 },
>  	{ X86_FEATURE_SGX_EDECCSSA,		CPUID_EAX, 11, 0x00000012, 0 },
>  	{ X86_FEATURE_HW_PSTATE,		CPUID_EDX,  7, 0x80000007, 0 },
>  	{ X86_FEATURE_CPB,			CPUID_EDX,  9, 0x80000007, 0 },
> diff --git a/tools/arch/x86/include/asm/cpufeatures.h b/tools/arch/x86/include/asm/cpufeatures.h
> index 6c2c152d8a67..ed0c0fa5822a 100644
> --- a/tools/arch/x86/include/asm/cpufeatures.h
> +++ b/tools/arch/x86/include/asm/cpufeatures.h
> @@ -481,6 +481,7 @@
>  #define X86_FEATURE_AMD_HETEROGENEOUS_CORES (21*32 + 6) /* Heterogeneous Core Topology */
>  #define X86_FEATURE_AMD_WORKLOAD_CLASS	(21*32 + 7) /* Workload Classification */
>  #define X86_FEATURE_PREFER_YMM		(21*32 + 8) /* Avoid ZMM registers due to downclocking */
> +#define X86_FEATURE_SGX_EUPDATESVN	(21*32 + 9) /* Support for ENCLS[EUPDATESVN] instruction */
>  
> 


Additionally, the new feature bit should be added to the CPUID dependency table:

--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -78,6 +78,7 @@ static const struct cpuid_dep cpuid_deps[] = {
        { X86_FEATURE_SGX_LC,                   X86_FEATURE_SGX       },
        { X86_FEATURE_SGX1,                     X86_FEATURE_SGX       },
        { X86_FEATURE_SGX2,                     X86_FEATURE_SGX1      },
+       { X86_FEATURE_SGX_EUPDATESVN,           X86_FEATURE_SGX1      },
        { X86_FEATURE_SGX_EDECCSSA,             X86_FEATURE_SGX1      },
        { X86_FEATURE_XFD,                      X86_FEATURE_XSAVES    },
        { X86_FEATURE_XFD,                      X86_FEATURE_XGETBV1   },