Re: [PATCH v10 05/28] x86/fpu/xstate: Add a new variable to indicate dynamic user states

[Thomas Gleixner]

On Sun, Oct 03 2021 at 22:35, Chang Seok Bae wrote:
> On Oct 1, 2021, at 06:16, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>> On Wed, Aug 25 2021 at 08:53, Chang S. Bae wrote:
>>> +/*
>>> + * This represents user xstates, a subset of xfeatures_mask_all, saved in a
>>> + * dynamic kernel XSAVE buffer.
>>> + */
>>> +u64 xfeatures_mask_user_dynamic __ro_after_init;
>>> +
>>> static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init =
>>> 	{ [ 0 ... XFEATURE_MAX - 1] = -1};
>>> static unsigned int xstate_sizes[XFEATURE_MAX] __ro_after_init =
>>> @@ -709,6 +715,7 @@ static int __init init_xstate_size(void)
>>> static void fpu__init_disable_system_xstate(void)
>>> {
>>> 	xfeatures_mask_all = 0;
>>> +	xfeatures_mask_user_dynamic = 0;
>> 
>> It's zero at boot already, isn't it?
>
> I thought of this as a safety net here when it was introduced.

A safety net for what? The compiler initializing the variable to 4711?