Re: [RFC v5 15/38] powerpc: helper function to read,write AMR,IAMR,UAMOR registers

[Balbir Singh]

On Wed,  5 Jul 2017 14:21:52 -0700
Ram Pai <linuxram@xxxxxxxxxx> wrote:

> Implements helper functions to read and write the key related
> registers; AMR, IAMR, UAMOR.
> 
> AMR register tracks the read,write permission of a key
> IAMR register tracks the execute permission of a key
> UAMOR register enables and disables a key
> 
> Signed-off-by: Ram Pai <linuxram@xxxxxxxxxx>
> ---
>  arch/powerpc/include/asm/book3s/64/pgtable.h |   60 ++++++++++++++++++++++++++
>  1 files changed, 60 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index 85bc987..435d6a7 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -428,6 +428,66 @@ static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
>  		pte_update(mm, addr, ptep, 0, _PAGE_PRIVILEGED, 1);
>  }
>  
> +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> +
> +#include <asm/reg.h>
> +static inline u64 read_amr(void)
> +{
> +	return mfspr(SPRN_AMR);
> +}
> +static inline void write_amr(u64 value)
> +{
> +	mtspr(SPRN_AMR, value);
> +}
> +static inline u64 read_iamr(void)
> +{
> +	return mfspr(SPRN_IAMR);
> +}
> +static inline void write_iamr(u64 value)
> +{
> +	mtspr(SPRN_IAMR, value);
> +}
> +static inline u64 read_uamor(void)
> +{
> +	return mfspr(SPRN_UAMOR);
> +}
> +static inline void write_uamor(u64 value)
> +{
> +	mtspr(SPRN_UAMOR, value);
> +}
> +
> +#else /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
> +
> +static inline u64 read_amr(void)
> +{
> +	WARN(1, "%s called with MEMORY PROTECTION KEYS disabled\n", __func__);
> +	return -1;
> +}

Why do we need to have a version here if we are going to WARN(), why not
let the compilation fail if called from outside of CONFIG_PPC64_MEMORY_PROTECTION_KEYS?
Is that the intention?

Balbir Singh