Re: [PATCH v3 2/2] virtio: replace arch_has_restricted_virtio_memory_access()

[Juergen Gross <jgross@xxxxxxxx>]

On 04.05.22 17:57, Juergen Gross wrote:
> Instead of using arch_has_restricted_virtio_memory_access() together
> with CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS, replace those
> with platform_has() and a new platform feature
> PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Could I get some feedback from the s390 side, please?


Juergen

> ---
> V2:
> - move setting of PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS in SEV case
>    to sev_setup_arch().
> V3:
> - remove Hyper-V chunk (Michael Kelley)
> - remove include virtio_config.h from mem_encrypt.c (Oleksandr Tyshchenko)
> - add comment for PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS (Oleksandr Tyshchenko)
> ---
>   arch/s390/Kconfig                |  1 -
>   arch/s390/mm/init.c              | 13 +++----------
>   arch/x86/Kconfig                 |  1 -
>   arch/x86/mm/mem_encrypt.c        |  7 -------
>   arch/x86/mm/mem_encrypt_amd.c    |  4 ++++
>   drivers/virtio/Kconfig           |  6 ------
>   drivers/virtio/virtio.c          |  5 ++---
>   include/linux/platform-feature.h |  6 +++++-
>   include/linux/virtio_config.h    |  9 ---------
>   9 files changed, 14 insertions(+), 38 deletions(-)
>
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index e084c72104f8..f97a22ae69a8 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -772,7 +772,6 @@ menu "Virtualization"
>   config PROTECTED_VIRTUALIZATION_GUEST
>         def_bool n
>         prompt "Protected virtualization guest support"
> -       select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
>         help
>           Select this option, if you want to be able to run this
>           kernel as a protected virtualization KVM guest.
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 86ffd0d51fd5..2c3b451813ed 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -31,6 +31,7 @@
>   #include <linux/cma.h>
>   #include <linux/gfp.h>
>   #include <linux/dma-direct.h>
> +#include <linux/platform-feature.h>
>   #include <asm/processor.h>
>   #include <linux/uaccess.h>
>   #include <asm/pgalloc.h>
> @@ -168,22 +169,14 @@ bool force_dma_unencrypted(struct device *dev)
>         return is_prot_virt_guest();
>   }
>   
> -#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> -
> -int arch_has_restricted_virtio_memory_access(void)
> -{
> -       return is_prot_virt_guest();
> -}
> -EXPORT_SYMBOL(arch_has_restricted_virtio_memory_access);
> -
> -#endif
> -
>   /* protected virtualization */
>   static void pv_init(void)
>   {
>         if (!is_prot_virt_guest())
>                 return;
>   
> +	platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
> +
>         /* make sure bounce buffers are shared */
>         swiotlb_force = SWIOTLB_FORCE;
>         swiotlb_init(1);
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 4bed3abf444d..eeb7c6c8eec5 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1515,7 +1515,6 @@ config X86_CPA_STATISTICS
>   config X86_MEM_ENCRYPT
>         select ARCH_HAS_FORCE_DMA_UNENCRYPTED
>         select DYNAMIC_PHYSICAL_MASK
> -       select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
>         def_bool n
>   
>   config AMD_MEM_ENCRYPT
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 50d209939c66..18a55a0f1ca2 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -12,7 +12,6 @@
>   #include <linux/swiotlb.h>
>   #include <linux/cc_platform.h>
>   #include <linux/mem_encrypt.h>
> -#include <linux/virtio_config.h>
>   
>   /* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
>   bool force_dma_unencrypted(struct device *dev)
> @@ -76,9 +75,3 @@ void __init mem_encrypt_init(void)
>   
>   	print_mem_encrypt_feature_info();
>   }
> -
> -int arch_has_restricted_virtio_memory_access(void)
> -{
> -       return cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT);
> -}
> -EXPORT_SYMBOL_GPL(arch_has_restricted_virtio_memory_access);
> diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
> index 6169053c2854..39b71084d36b 100644
> --- a/arch/x86/mm/mem_encrypt_amd.c
> +++ b/arch/x86/mm/mem_encrypt_amd.c
> @@ -21,6 +21,7 @@
>   #include <linux/dma-mapping.h>
>   #include <linux/virtio_config.h>
>   #include <linux/cc_platform.h>
> +#include <linux/platform-feature.h>
>   
>   #include <asm/tlbflush.h>
>   #include <asm/fixmap.h>
> @@ -206,6 +207,9 @@ void __init sev_setup_arch(void)
>         size = total_mem * 6 / 100;
>         size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
>         swiotlb_adjust_size(size);
> +
> +       /* Set restricted memory access for virtio. */
> +       platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
>   }
>   
>   static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index b5adf6abd241..a6dc8b5846fe 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -6,12 +6,6 @@ config VIRTIO
>           bus, such as CONFIG_VIRTIO_PCI, CONFIG_VIRTIO_MMIO, CONFIG_RPMSG
>           or CONFIG_S390_GUEST.
>   
> -config ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> -       bool
> -       help
> -         This option is selected if the architecture may need to enforce
> -         VIRTIO_F_ACCESS_PLATFORM
> -
>   config VIRTIO_PCI_LIB
>         tristate
>         help
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 22f15f444f75..371e16b18381 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -5,6 +5,7 @@
>   #include <linux/module.h>
>   #include <linux/idr.h>
>   #include <linux/of.h>
> +#include <linux/platform-feature.h>
>   #include <uapi/linux/virtio_ids.h>
>   
>   /* Unique numbering for virtio devices. */
> @@ -170,12 +171,10 @@ EXPORT_SYMBOL_GPL(virtio_add_status);
>   static int virtio_features_ok(struct virtio_device *dev)
>   {
>         unsigned status;
> -       int ret;
>   
>   	might_sleep();
>   
> -	ret = arch_has_restricted_virtio_memory_access();
> -       if (ret) {
> +       if (platform_has(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS)) {
>                 if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
>                         dev_warn(&dev->dev,
>                                  "device must provide VIRTIO_F_VERSION_1\n");
> diff --git a/include/linux/platform-feature.h b/include/linux/platform-feature.h
> index 6ed859928b97..b2f48be999fa 100644
> --- a/include/linux/platform-feature.h
> +++ b/include/linux/platform-feature.h
> @@ -6,7 +6,11 @@
>   #include <asm/platform-feature.h>
>   
>   /* The platform features are starting with the architecture specific ones. */
> -#define PLATFORM_FEAT_N                                (0 + 
> PLATFORM_ARCH_FEAT_N)
> +
> +/* Used to enable platform specific DMA handling for virtio devices. */
> +#define PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS  (0 + PLATFORM_ARCH_FEAT_N)
> +
> +#define PLATFORM_FEAT_N                                (1 + 
> PLATFORM_ARCH_FEAT_N)
>   
>   void platform_set(unsigned int feature);
>   void platform_clear(unsigned int feature);
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index b341dd62aa4d..79498298519d 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -559,13 +559,4 @@ static inline void virtio_cwrite64(struct virtio_device 
> *vdev,
>                 _r;                                                     \
>         })
>   
> -#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> -int arch_has_restricted_virtio_memory_access(void);
> -#else
> -static inline int arch_has_restricted_virtio_memory_access(void)
> -{
> -       return 0;
> -}
> -#endif /* CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS */
> -
>   #endif /* _LINUX_VIRTIO_CONFIG_H */

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