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

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Message-ID: <82a9f0c4-7e6d-477a-bc6e-6dcb046b25fd@intel.com>
Date: Fri, 5 Jan 2024 16:16:53 +0800
From: "Yang, Weijiang" <weijiang.yang@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
CC: "Hansen, Dave" <dave.hansen@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>, "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 1/5/2024 6:47 AM, Edgecombe, Rick P wrote:
> 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.

Ah, this is another unused variable after introduce fpu_guest_cfg.*, should be replaced by
fpu_guest_cfg.default_size. Thanks for caching it!