linux-kernel - Re: [patch V2 04/14] x86/pkru: Make the fpinit state update work

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Date:   Mon, 7 Jun 2021 17:18:38 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        stable@...r.kernel.org
Subject: Re: [patch V2 04/14] x86/pkru: Make the fpinit state update work

On Sun, Jun 06, 2021 at 01:47:46AM +0200, Thomas Gleixner wrote:
> @@ -120,6 +121,8 @@ void __init check_bugs(void)
>  
>  	arch_smt_update();
>  
> +	pkru_propagate_default();

I guess this fits better at the end of identify_boot_cpu(), which is
pretty close to here, in the boot order.

Regardless, that function check_bugs() needs cleaning up as it has
collected a lot more stuff than just checking the bugs nasty.

> +void pkru_propagate_default(void)
>  {
> -	u32 init_pkru_value_snapshot = READ_ONCE(init_pkru_value);
> +	struct pkru_state *pk;
> +
> +	if (!boot_cpu_has(X86_FEATURE_OSPKE))

cpu_feature_enabled()

> +		return;
>  	/*
> -	 * Override the PKRU state that came from 'init_fpstate'
> -	 * with the baseline from the process.
> +	 * Force XFEATURE_PKRU to be set in the header otherwise
> +	 * get_xsave_addr() does not work and it needs to be set
> +	 * to make XRSTOR(S) load it.
>  	 */
> -	write_pkru(init_pkru_value_snapshot);
> +	init_fpstate.xsave.header.xfeatures |= XFEATURE_MASK_PKRU;
> +	pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU);
> +	pk->pkru = READ_ONCE(init_pkru_value);
>  }

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette