linux-kernel - Re: [PATCH RFC V3 2/9] x86/fpu: Refactor arch_set_user_pkey

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Date:   Fri, 16 Oct 2020 12:57:43 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     ira.weiny@...el.com
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Fenghua Yu <fenghua.yu@...el.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH RFC V3 2/9] x86/fpu: Refactor arch_set_user_pkey_access()
 for PKS support

On Fri, Oct 09, 2020 at 12:42:51PM -0700, ira.weiny@...el.com wrote:
> From: Fenghua Yu <fenghua.yu@...el.com>
> 
> Define a helper, update_pkey_val(), which will be used to support both
> Protection Key User (PKU) and the new Protection Key for Supervisor
> (PKS) in subsequent patches.
> 
> Co-developed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> ---
>  arch/x86/include/asm/pkeys.h |  2 ++
>  arch/x86/kernel/fpu/xstate.c | 22 ++++------------------
>  arch/x86/mm/pkeys.c          | 21 +++++++++++++++++++++
>  3 files changed, 27 insertions(+), 18 deletions(-)

This is not from Fenghua.

  https://lkml.kernel.org/r/20200717085442.GX10769@hirez.programming.kicks-ass.net

This is your patch based on the code I wrote.

> diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
> index f5efb4007e74..3cf8f775f36d 100644
> --- a/arch/x86/mm/pkeys.c
> +++ b/arch/x86/mm/pkeys.c
> @@ -208,3 +208,24 @@ static __init int setup_init_pkru(char *opt)
>  	return 1;
>  }
>  __setup("init_pkru=", setup_init_pkru);
> +
> +/*
> + * Update the pk_reg value and return it.
> + *
> + * Kernel users use the same flags as user space:
> + *     PKEY_DISABLE_ACCESS
> + *     PKEY_DISABLE_WRITE
> + */
> +u32 update_pkey_val(u32 pk_reg, int pkey, unsigned int flags)
> +{
> +	int pkey_shift = pkey * PKR_BITS_PER_PKEY;
> +
> +	pk_reg &= ~(((1 << PKR_BITS_PER_PKEY) - 1) << pkey_shift);
> +
> +	if (flags & PKEY_DISABLE_ACCESS)
> +		pk_reg |= PKR_AD_BIT << pkey_shift;
> +	if (flags & PKEY_DISABLE_WRITE)
> +		pk_reg |= PKR_WD_BIT << pkey_shift;
> +
> +	return pk_reg;
> +}
> -- 
> 2.28.0.rc0.12.gb6a658bd00c9
>