Please split the swiotlb changes into a separate patch from the
consumer.

 }
+
+/*
+ * hv_map_memory - map memory to extra space in the AMD SEV-SNP Isolation VM.
+ */
+unsigned long hv_map_memory(unsigned long addr, unsigned long size)
+{
+	unsigned long *pfns = kcalloc(size / HV_HYP_PAGE_SIZE,
+				      sizeof(unsigned long),
+		       GFP_KERNEL);
+	unsigned long vaddr;
+	int i;
+
+	if (!pfns)
+		return (unsigned long)NULL;
+
+	for (i = 0; i < size / HV_HYP_PAGE_SIZE; i++)
+		pfns[i] = virt_to_hvpfn((void *)addr + i * HV_HYP_PAGE_SIZE) +
+			(ms_hyperv.shared_gpa_boundary >> HV_HYP_PAGE_SHIFT);
+
+	vaddr = (unsigned long)vmap_pfn(pfns, size / HV_HYP_PAGE_SIZE,
+					PAGE_KERNEL_IO);
+	kfree(pfns);
+
+	return vaddr;

This seems to miss a 'select VMAP_PFN'.  But more importantly I don't
think this actually works.  Various DMA APIs do expect a struct page
backing, so how is this going to work with say dma_mmap_attrs or
dma_get_sgtable_attrs?

+static unsigned long __map_memory(unsigned long addr, unsigned long size)
+{
+	if (hv_is_isolation_supported())
+		return hv_map_memory(addr, size);
+
+	return addr;
+}
+
+static void __unmap_memory(unsigned long addr)
+{
+	if (hv_is_isolation_supported())
+		hv_unmap_memory(addr);
+}
+
+unsigned long set_memory_decrypted_map(unsigned long addr, unsigned long size)
+{
+	if (__set_memory_enc_dec(addr, size / PAGE_SIZE, false))
+		return (unsigned long)NULL;
+
+	return __map_memory(addr, size);
+}
+
+int set_memory_encrypted_unmap(unsigned long addr, unsigned long size)
+{
+	__unmap_memory(addr);
+	return __set_memory_enc_dec(addr, size / PAGE_SIZE, true);
+}

Why this obsfucation into all kinds of strange helpers?  Also I think
we want an ops vectors (or alternative calls) instead of the random
if checks here.

+ * @vstart:	The virtual start address of the swiotlb memory pool. The swiotlb
+ *		memory pool may be remapped in the memory encrypted case and store

Normall we'd call this vaddr or cpu_addr.

-	set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT);
-	memset(vaddr, 0, bytes);
+	mem->vstart = (void *)set_memory_decrypted_map((unsigned long)vaddr, bytes);

Please always pass kernel virtual addresses as pointers.

And I think these APIs might need better names, e.g.

arch_dma_map_decrypted and arch_dma_unmap_decrypted.

Also these will need fallback versions for non-x86 architectures that
currently use memory encryption.