linux-kernel - Re: [PATCH v9 06/27] x86/fpu/xstate: Create guest fpstate with guest specific config

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Date: Tue, 30 Jan 2024 22:54:20 +0800
From: "Yang, Weijiang" <weijiang.yang@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
CC: "Hansen, Dave" <dave.hansen@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "yuan.yao@...ux.intel.com" <yuan.yao@...ux.intel.com>,
	"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 v9 06/27] x86/fpu/xstate: Create guest fpstate with guest
 specific config

On 1/30/2024 9:38 AM, Edgecombe, Rick P wrote:
> On Tue, 2024-01-23 at 18:41 -0800, Yang Weijiang wrote:
>> -bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
>> +static struct fpstate *__fpu_alloc_init_guest_fpstate(struct
>> fpu_guest *gfpu)
>>   {
>>          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);
> Minor, I'm not sure the extra char warrants changing it to a wrapped
> line, but that's just my personal opinion.
>
>> +
>>          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           = fpu_guest_cfg.default_size;
>> +       fpstate->xfeatures      = fpu_guest_cfg.default_features;
>> +       fpstate->user_size      = fpu_user_cfg.default_size;
>> +       fpstate->user_xfeatures = fpu_user_cfg.default_features;
>> +       fpstate->xfd            = 0;
>>   
>> -       /* Leave xfd to 0 (the reset value defined by spec) */
>> -       __fpstate_reset(fpstate, 0);
>>          fpstate_init_user(fpstate);
>>          fpstate->is_valloc      = true;
>>          fpstate->is_guest       = true;
>>   
>>          gfpu->fpstate           = fpstate;
>> -       gfpu->xfeatures         = fpu_user_cfg.default_features;
>> -       gfpu->perm              = fpu_user_cfg.default_features;
>> +       gfpu->xfeatures         = fpu_guest_cfg.default_features;
>> +       gfpu->perm              = fpu_guest_cfg.default_features;
>> +
>> +       return fpstate;
>> +}
>> +
>> +bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
>> +{
>> +       struct fpstate *fpstate;
>> +
>> +       fpstate = __fpu_alloc_init_guest_fpstate(gfpu);
> The above two statements could be just one line and still even fit
> under 80 chars.

Indeed, the variable is redundant, I'll remove it, thanks!

>
> All the same,
>
> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
>
>> +
>> +       if (!fpstate)
>> +               return false;
>>