linux-kernel - Re: [PATCH 04/19] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states

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Date:   Thu, 16 Jun 2022 12:27:47 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yang Weijiang <weijiang.yang@...el.com>
Cc:     pbonzini@...hat.com, seanjc@...gle.com, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        rick.p.edgecombe@...el.com, Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 04/19] x86/fpu/xstate: Introduce CET MSR and XSAVES
 supervisor states

On Thu, Jun 16, 2022 at 04:46:28AM -0400, Yang Weijiang wrote:
> diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
> index eb7cd1139d97..03aa98fb9c2b 100644
> --- a/arch/x86/include/asm/fpu/types.h
> +++ b/arch/x86/include/asm/fpu/types.h
> @@ -115,8 +115,8 @@ enum xfeature {
>  	XFEATURE_PT_UNIMPLEMENTED_SO_FAR,
>  	XFEATURE_PKRU,
>  	XFEATURE_PASID,
> -	XFEATURE_RSRVD_COMP_11,
> -	XFEATURE_RSRVD_COMP_12,
> +	XFEATURE_CET_USER,
> +	XFEATURE_CET_KERNEL_UNIMPLEMENTED_SO_FAR,
>  	XFEATURE_RSRVD_COMP_13,
>  	XFEATURE_RSRVD_COMP_14,
>  	XFEATURE_LBR,
> @@ -138,6 +138,8 @@ enum xfeature {
>  #define XFEATURE_MASK_PT		(1 << XFEATURE_PT_UNIMPLEMENTED_SO_FAR)
>  #define XFEATURE_MASK_PKRU		(1 << XFEATURE_PKRU)
>  #define XFEATURE_MASK_PASID		(1 << XFEATURE_PASID)
> +#define XFEATURE_MASK_CET_USER		(1 << XFEATURE_CET_USER)
> +#define XFEATURE_MASK_CET_KERNEL	(1 << XFEATURE_CET_KERNEL_UNIMPLEMENTED_SO_FAR)
>  #define XFEATURE_MASK_LBR		(1 << XFEATURE_LBR)
>  #define XFEATURE_MASK_XTILE_CFG		(1 << XFEATURE_XTILE_CFG)
>  #define XFEATURE_MASK_XTILE_DATA	(1 << XFEATURE_XTILE_DATA)

I'm not sure about that UNIMPLEMENTED_SO_FAR thing, that is, I'm
thinking we *never* want XSAVE managed S_CET.