linux-kernel - Re: [PATCH v7 06/26] x86/fpu/xstate: Create guest fpstate with guest specific config

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Date:   Tue, 28 Nov 2023 15:19:42 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Yang, Weijiang" <weijiang.yang@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>
CC:     "john.allen@....com" <john.allen@....com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Gao, Chao" <chao.gao@...el.com>,
        "mlevitsk@...hat.com" <mlevitsk@...hat.com>
Subject: Re: [PATCH v7 06/26] x86/fpu/xstate: Create guest fpstate with guest
 specific config

On Fri, 2023-11-24 at 00:53 -0500, Yang Weijiang wrote:
> +static struct fpstate *__fpu_alloc_init_guest_fpstate(struct
> fpu_guest *gfpu)
>  {
> +       bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED);
> +       unsigned int gfpstate_size, size;
>         struct fpstate *fpstate;
> -       unsigned int size;
>  
> -       size = fpu_user_cfg.default_size + ALIGN(offsetof(struct
> fpstate, regs), 64);
> +       /*
> +        * fpu_guest_cfg.default_features includes all enabled
> xfeatures
> +        * except the user dynamic xfeatures. If the user dynamic
> xfeatures
> +        * are enabled, the guest fpstate will be re-allocated to
> hold all
> +        * guest enabled xfeatures, so omit user dynamic xfeatures
> here.
> +        */
> +       gfpstate_size =
> xstate_calculate_size(fpu_guest_cfg.default_features,
> +                                             compacted);

Why not fpu_guest_cfg.default_size here?

> +
> +       size = gfpstate_size + ALIGN(offsetof(struct fpstate, regs),
> 64);