[PATCH v6 01/20] s390: Expose protected virtualization through cc_platform_has()

[JAEHOON KIM]

On 6/4/2026 3:39 AM, Aneesh Kumar K.V (Arm) wrote:
> Protected virtualization guests use memory encryption, so advertise that to
> the rest of the kernel through cc_platform_has(CC_ATTR_MEM_ENCRYPT).
>
> s390 already forces DMA mappings to be unencrypted for protected
> virtualization guests through force_dma_unencrypted(). Add
> ARCH_HAS_CC_PLATFORM and provide the matching cc_platform_has()
> implementation
>
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar at kernel.org>

Tested-by: Jaehoon Kim <jhkim at linux.ibm.com>

Tested on s390 PV guest with swiotlb_dynamic configuration. SWIOTLB
bounce buffer allocation and dynamic pool management work correctly.
Also concurrent I/O stress completed successfully.

Thanks,
Jaehoon.

> ---
> Cc: Halil Pasic <pasic at linux.ibm.com>
> Cc: Matthew Rosato <mjrosato at linux.ibm.com>
> Cc: Jaehoon  Kim <jhkim at linux.ibm.com>
> ---
>   arch/s390/Kconfig   |  1 +
>   arch/s390/mm/init.c | 14 ++++++++++++++
>   2 files changed, 15 insertions(+)
>
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index ecbcbb781e40..9b5e6029e043 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -87,6 +87,7 @@ config S390
>   	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
>   	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
>   	select ARCH_HAS_CC_CAN_LINK
> +	select ARCH_HAS_CC_PLATFORM
>   	select ARCH_HAS_CPU_FINALIZE_INIT
>   	select ARCH_HAS_CURRENT_STACK_POINTER
>   	select ARCH_HAS_DEBUG_VIRTUAL
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 1f72efc2a579..ad3c6d92b801 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -50,6 +50,7 @@
>   #include <linux/virtio_anchor.h>
>   #include <linux/virtio_config.h>
>   #include <linux/execmem.h>
> +#include <linux/cc_platform.h>
>   
>   pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(".bss..swapper_pg_dir");
>   pgd_t invalid_pg_dir[PTRS_PER_PGD] __section(".bss..invalid_pg_dir");
> @@ -140,6 +141,19 @@ bool force_dma_unencrypted(struct device *dev)
>   	return is_prot_virt_guest();
>   }
>   
> +
> +bool cc_platform_has(enum cc_attr attr)
> +{
> +	switch (attr) {
> +	case CC_ATTR_MEM_ENCRYPT:
> +		return is_prot_virt_guest();
> +
> +	default:
> +		return false;
> +	}
> +}
> +EXPORT_SYMBOL_GPL(cc_platform_has);
> +
>   /* protected virtualization */
>   static void __init pv_init(void)
>   {