s390/mm: force swiotlb for protected virtualization

On s390, protected virtualization guests have to use bounced I/O
buffers. That requires some plumbing.

Let us make sure, any device that uses DMA API with direct ops correctly
is spared from the problems, that a hypervisor attempting I/O to a
non-shared page would bring.

Signed-off-by: Halil Pasic <[e-mail]>
Reviewed-by: Claudio Imbrenda <[e-mail]>
Reviewed-by: Michael Mueller <[e-mail]>
Tested-by: Michael Mueller <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>

arch/s390/Kconfig

···
 # SPDX-License-Identifier: GPL-2.0
+config ARCH_HAS_MEM_ENCRYPT
+        def_bool y
+
 config MMU
 	def_bool y
 
···
 	select VIRT_CPU_ACCOUNTING
 	select ARCH_HAS_SCALED_CPUTIME
 	select HAVE_NMI
+	select SWIOTLB
 
 
 config SCHED_OMIT_FRAME_POINTER

arch/s390/include/asm/mem_encrypt.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef S390_MEM_ENCRYPT_H__
+#define S390_MEM_ENCRYPT_H__
+
+#ifndef __ASSEMBLY__
+
+#define sme_me_mask	0ULL
+
+static inline bool sme_active(void) { return false; }
+extern bool sev_active(void);
+
+int set_memory_encrypted(unsigned long addr, int numpages);
+int set_memory_decrypted(unsigned long addr, int numpages);
+
+#endif	/* __ASSEMBLY__ */
+
+#endif	/* S390_MEM_ENCRYPT_H__ */

arch/s390/mm/init.c

···
 #include <linux/mman.h>
 #include <linux/mm.h>
 #include <linux/swap.h>
+#include <linux/swiotlb.h>
 #include <linux/smp.h>
 #include <linux/init.h>
 #include <linux/pagemap.h>
···
 #include <linux/export.h>
 #include <linux/cma.h>
 #include <linux/gfp.h>
+#include <linux/dma-mapping.h>
 #include <asm/processor.h>
 #include <linux/uaccess.h>
 #include <asm/pgtable.h>
···
 #include <asm/sclp.h>
 #include <asm/set_memory.h>
 #include <asm/kasan.h>
+#include <asm/dma-mapping.h>
+#include <asm/uv.h>
 
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
 
···
 	pr_info("Write protected read-only-after-init data: %luk\n", size >> 10);
 }
 
+int set_memory_encrypted(unsigned long addr, int numpages)
+{
+	int i;
+
+	/* make specified pages unshared, (swiotlb, dma_free) */
+	for (i = 0; i < numpages; ++i) {
+		uv_remove_shared(addr);
+		addr += PAGE_SIZE;
+	}
+	return 0;
+}
+
+int set_memory_decrypted(unsigned long addr, int numpages)
+{
+	int i;
+	/* make specified pages shared (swiotlb, dma_alloca) */
+	for (i = 0; i < numpages; ++i) {
+		uv_set_shared(addr);
+		addr += PAGE_SIZE;
+	}
+	return 0;
+}
+
+/* are we a protected virtualization guest? */
+bool sev_active(void)
+{
+	return is_prot_virt_guest();
+}
+
+/* protected virtualization */
+static void pv_init(void)
+{
+	if (!is_prot_virt_guest())
+		return;
+
+	/* make sure bounce buffers are shared */
+	swiotlb_init(1);
+	swiotlb_update_mem_attributes();
+	swiotlb_force = SWIOTLB_FORCE;
+}
+
 void __init mem_init(void)
 {
 	cpumask_set_cpu(0, &init_mm.context.cpu_attach_mask);
···
 
 	set_max_mapnr(max_low_pfn);
         high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
+
+	pv_init();
 
 	/* Setup guest page hinting */
 	cmma_init();