Re: [PATCH v5 02/20] [DO NOT MERGE] s390: Expose protected virtualization through cc_platform_has()

[JAEHOON KIM <jhkim@linux.ibm.com>]

On 5/21/2026 11:27 PM, 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@kernel.org>
> ---
> Cc: Halil Pasic <pasic@linux.ibm.com>
> Cc: Matthew Rosato <mjrosato@linux.ibm.com>
> Cc: Jaehoon  Kim <jhkim@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)
>   {

Hello Aneesh,

Thanks for adding this s390 support patch.

The previous v4 series broke virtio initialization and caused boot
failures on s390. With this patch in v5, the issue is completely
resolved and virtio devices now initialize successfully and are
working well.

I'm going to do some more testing and will let you know if I run
into any issues.

Thanks,
Jaehoon.