linux-kernel - Re: [PATCH v8 06/26] x86/fpu/xstate: Create guest fpstate with guest specific config

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Date: Thu, 4 Jan 2024 22:47:16 +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 v8 06/26] x86/fpu/xstate: Create guest fpstate with guest
 specific config

On Thu, 2023-12-21 at 09:02 -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_size is initialized to hold 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.
> +        */
> +       size = fpu_guest_cfg.default_size +
> +              ALIGN(offsetof(struct fpstate, regs), 64);
> +
>         fpstate = vzalloc(size);
>         if (!fpstate)
> -               return false;
> +               return NULL;
> +       /*
> +        * Initialize sizes and feature masks, use fpu_user_cfg.*
> +        * for user_* settings for compatibility of exiting uAPIs.
> +        */
> +       fpstate->size           = gfpstate_size;

gfpstate_size is used uninitialized.