virtio: replace arch_has_restricted_virtio_memory_access()

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 <[e-mail]>
Reviewed-by: Oleksandr Tyshchenko <[e-mail]>
Tested-by: Oleksandr Tyshchenko <[e-mail]> # Arm64 only
Reviewed-by: Christoph Hellwig <[e-mail]>
Acked-by: Borislav Petkov <[e-mail]>

arch/s390/Kconfig

···
 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.

arch/s390/mm/init.c

···
 #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>
···
 	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_init(true, SWIOTLB_FORCE | SWIOTLB_VERBOSE);

arch/x86/Kconfig

···
 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

arch/x86/mm/mem_encrypt.c

···
 #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)
···
 
 	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);

arch/x86/mm/mem_encrypt_amd.c

···
 #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>
···
 	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)

drivers/virtio/Kconfig

···
 	  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

drivers/virtio/virtio.c

···
 #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. */
···
 static int virtio_features_ok(struct virtio_device *dev)
 {
 	unsigned int 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");

include/linux/platform-feature.h

···
 #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);

include/linux/virtio_config.h

···
 		_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 */