From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: Xin Li <xin3.li@intel.com>, <linux-kernel@vger.kernel.org>,
<x86@kernel.org>
Cc: <tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>,
<dave.hansen@linux.intel.com>, <hpa@zytor.com>,
<peterz@infradead.org>
Subject: Re: [PATCH v2 1/6] x86/cpufeature: add cpu feature bit for LKGS
Date: Tue, 11 Oct 2022 18:40:26 -0700 [thread overview]
Message-ID: <cca7e8ec-9fa0-7517-12d2-b0fd115bb9e9@intel.com> (raw)
In-Reply-To: <20221010190159.11920-2-xin3.li@intel.com>
On 10/10/2022 12:01 PM, Xin Li wrote:
>
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index ef4775c6db01..459fb0c21dd4 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -308,6 +308,7 @@
> /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
> #define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */
> #define X86_FEATURE_AVX512_BF16 (12*32+ 5) /* AVX512 BFLOAT16 instructions */
> +#define X86_FEATURE_LKGS (12*32+ 18) /* Load "kernel" (userspace) gs */
The spec says [1]:
"Execution of LKGS causes an invalid-opcode exception (#UD) if CPL >
0."
Perhaps userspace has no interest in this. Then, we can add "" not to
show "lkgs" in /proc/cpuinfo:
+#define X86_FEATURE_LKGS (12*32+ 18) /* "" Load "kernel"
(userspace) gs */
Thanks,
Chang
[1] https://cdrdv2.intel.com/v1/dl/getContent/678938
next prev parent reply other threads:[~2022-10-12 1:40 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-10 19:01 [PATCH v2 0/6] Enable LKGS instruction Xin Li
2022-10-10 19:01 ` [PATCH v2 1/6] x86/cpufeature: add cpu feature bit for LKGS Xin Li
2022-10-12 1:40 ` Chang S. Bae [this message]
2022-10-13 19:35 ` Li, Xin3
2022-10-13 20:05 ` H. Peter Anvin
2022-10-10 19:01 ` [PATCH v2 2/6] x86/opcode: add LKGS instruction to x86-opcode-map Xin Li
2022-10-10 19:01 ` [PATCH v2 3/6] x86/gsseg: make asm_load_gs_index() take an u16 Xin Li
2022-10-10 19:01 ` [PATCH v2 4/6] x86/gsseg: move local_irq_save/restore() into asm_load_gs_index() Xin Li
2022-10-10 19:01 ` [PATCH v2 5/6] x86/gsseg: move load_gs_index() to its own header file Xin Li
2022-10-10 19:01 ` [PATCH v2 6/6] x86/gsseg: use the LKGS instruction if available for load_gs_index() Xin Li
2022-10-11 3:51 ` Brian Gerst
2022-10-11 4:20 ` H. Peter Anvin
2022-10-11 17:12 ` Li, Xin3
2022-10-11 0:59 ` [PATCH v2 0/6] Enable LKGS instruction H. Peter Anvin
2022-10-11 3:51 ` Li, Xin3
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