Re: [PATCH RFC V3 2/9] x86/fpu: Refactor arch_set_user_pkey_access() for PKS support

[Peter Zijlstra]

On Fri, Oct 09, 2020 at 12:42:51PM -0700, ira.weiny@xxxxxxxxx wrote:
> From: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> 
> 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@xxxxxxxxx>
> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> ---
>  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@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

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
>