Re: [PATCH v5 08/10] arm64: realm: Move Realm memory encryption ops to RSI code

[Will Deacon]

On Mon, Jul 06, 2026 at 11:34:30AM +0530, Aneesh Kumar K.V (Arm) wrote:
> Realm memory encryption callbacks are CCA-specific. Keep the Realm callback
> registration with the RSI initialization code instead of pageattr.c, which
> only needs to provide the low-level page-attribute transition helper.
> 
> Export __set_memory_enc_dec() within arm64 so the RSI code can wrap it with
> the Realm-specific encrypt/decrypt callbacks and warning policy.
> 
> No functional changes in this patch.
> 
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@xxxxxxxxxx>
> ---
>  arch/arm64/include/asm/mem_encrypt.h |  3 +--
>  arch/arm64/kernel/rsi.c              | 34 +++++++++++++++++++++++++
>  arch/arm64/mm/pageattr.c             | 38 +---------------------------
>  3 files changed, 36 insertions(+), 39 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/mem_encrypt.h b/arch/arm64/include/asm/mem_encrypt.h
> index 314b2b52025f..f6325f30e844 100644
> --- a/arch/arm64/include/asm/mem_encrypt.h
> +++ b/arch/arm64/include/asm/mem_encrypt.h
> @@ -15,8 +15,7 @@ int arm64_mem_crypt_ops_register(const struct arm64_mem_crypt_ops *ops);
>  
>  int set_memory_encrypted(unsigned long addr, int numpages);
>  int set_memory_decrypted(unsigned long addr, int numpages);
> -
> -int realm_register_memory_enc_ops(void);
> +int __set_memory_enc_dec(unsigned long addr, int numpages, bool encrypt);
>  
>  static inline bool force_dma_unencrypted(struct device *dev)
>  {
> diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
> index 1fb2abd79800..5c566700974c 100644
> --- a/arch/arm64/kernel/rsi.c
> +++ b/arch/arm64/kernel/rsi.c
> @@ -143,6 +143,40 @@ static int realm_ioremap_hook(phys_addr_t phys, size_t size, pgprot_t *prot)
>  	return 0;
>  }
>  
> +static int realm_set_memory_encrypted(unsigned long addr, int numpages)
> +{
> +	int ret = __set_memory_enc_dec(addr, numpages, true);
> +
> +	/*
> +	 * If the request to change state fails, then the only sensible cause
> +	 * of action for the caller is to leak the memory
> +	 */
> +	WARN(ret, "Failed to encrypt memory, %d pages will be leaked",
> +	     numpages);
> +
> +	return ret;
> +}
> +
> +static int realm_set_memory_decrypted(unsigned long addr, int numpages)
> +{
> +	int ret = __set_memory_enc_dec(addr, numpages, false);
> +
> +	WARN(ret, "Failed to decrypt memory, %d pages will be leaked",
> +	     numpages);
> +
> +	return ret;
> +}
> +
> +static const struct arm64_mem_crypt_ops realm_crypt_ops = {
> +	.encrypt = realm_set_memory_encrypted,
> +	.decrypt = realm_set_memory_decrypted,
> +};
> +
> +static int realm_register_memory_enc_ops(void)
> +{
> +	return arm64_mem_crypt_ops_register(&realm_crypt_ops);
> +}

It's good to move these out of pageattr.c but I still don't think any
of this stuff should be in arch/arm64. This is a firmware interface,
just like PSCI, so it should live in drivers/firmware/ along with all
the other Arm firmware interfaces (SDEI, FFA, SCMI, PSCI, SMCCC, ...).

Will