Merge tag 'for-linus-5.19a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:

 - a small cleanup removing "export" of an __init function

 - a small series adding a new infrastructure for platform flags

 - a series adding generic virtio support for Xen guests (frontend side)

* tag 'for-linus-5.19a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: unexport __init-annotated xen_xlate_map_ballooned_pages()
  arm/xen: Assign xen-grant DMA ops for xen-grant DMA devices
  xen/grant-dma-ops: Retrieve the ID of backend's domain for DT devices
  xen/grant-dma-iommu: Introduce stub IOMMU driver
  dt-bindings: Add xen,grant-dma IOMMU description for xen-grant DMA ops
  xen/virtio: Enable restricted memory access using Xen grant mappings
  xen/grant-dma-ops: Add option to restrict memory access under Xen
  xen/grants: support allocating consecutive grants
  arm/xen: Introduce xen_setup_dma_ops()
  virtio: replace arch_has_restricted_virtio_memory_access()
  kernel: add platform_has() infrastructure

Documentation/devicetree/bindings/iommu/xen,grant-dma.yaml

+# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iommu/xen,grant-dma.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Xen specific IOMMU for virtualized devices (e.g. virtio)
+
+maintainers:
+  - Stefano Stabellini <sstabellini@kernel.org>
+
+description:
+  The Xen IOMMU represents the Xen grant table interface. Grant mappings
+  are to be used with devices connected to the Xen IOMMU using the "iommus"
+  property, which also specifies the ID of the backend domain.
+  The binding is required to restrict memory access using Xen grant mappings.
+
+properties:
+  compatible:
+    const: xen,grant-dma
+
+  '#iommu-cells':
+    const: 1
+    description:
+      The single cell is the domid (domain ID) of the domain where the backend
+      is running.
+
+required:
+  - compatible
+  - "#iommu-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    iommu {
+        compatible = "xen,grant-dma";
+        #iommu-cells = <1>;
+    };

MAINTAINERS

@@ -15831,6 +15831,14 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/iio/chemical/plantower,pms7003.yaml
 F:	drivers/iio/chemical/pms7003.c
 
+PLATFORM FEATURE INFRASTRUCTURE
+M:	Juergen Gross <jgross@suse.com>
+S:	Maintained
+F:	arch/*/include/asm/platform-feature.h
+F:	include/asm-generic/platform-feature.h
+F:	include/linux/platform-feature.h
+F:	kernel/platform-feature.c
+
 PLDMFW LIBRARY
 M:	Jacob Keller <jacob.e.keller@intel.com>
 S:	Maintained

arch/arm/include/asm/xen/xen-ops.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#include <xen/arm/xen-ops.h>

arch/arm/mm/dma-mapping.c

@@ -33,7 +33,7 @@
 #include <asm/dma-iommu.h>
 #include <asm/mach/map.h>
 #include <asm/system_info.h>
-#include <xen/swiotlb-xen.h>
+#include <asm/xen/xen-ops.h>
 
 #include "dma.h"
 #include "mm.h"
@@ -2287,10 +2287,7 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 
 	set_dma_ops(dev, dma_ops);
 
-#ifdef CONFIG_XEN
-	if (xen_initial_domain())
-		dev->dma_ops = &xen_swiotlb_dma_ops;
-#endif
+	xen_setup_dma_ops(dev);
 	dev->archdata.dma_ops_setup = true;
 }
 

arch/arm/xen/enlighten.c

@@ -443,6 +443,8 @@ static int __init xen_guest_init(void)
 	if (!xen_domain())
 		return 0;
 
+	xen_set_restricted_virtio_memory_access();
+
 	if (!acpi_disabled)
 		xen_acpi_guest_init();
 	else

arch/arm64/include/asm/xen/xen-ops.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#include <xen/arm/xen-ops.h>

arch/arm64/mm/dma-mapping.c

@@ -9,9 +9,9 @@
 #include <linux/dma-map-ops.h>
 #include <linux/dma-iommu.h>
 #include <xen/xen.h>
-#include <xen/swiotlb-xen.h>
 
 #include <asm/cacheflush.h>
+#include <asm/xen/xen-ops.h>
 
 void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
 		enum dma_data_direction dir)
@@ -52,8 +52,5 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 	if (iommu)
 		iommu_setup_dma_ops(dev, dma_base, dma_base + size - 1);
 
-#ifdef CONFIG_XEN
-	if (xen_swiotlb_detect())
-		dev->dma_ops = &xen_swiotlb_dma_ops;
-#endif
+	xen_setup_dma_ops(dev);
 }

arch/s390/Kconfig

@@ -769,7 +769,6 @@ 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.

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_init(true, SWIOTLB_FORCE | SWIOTLB_VERBOSE);
 	swiotlb_update_mem_attributes();

arch/x86/Kconfig

@@ -1542,7 +1542,6 @@ 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

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)
@@ -87,9 +86,3 @@ 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);

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>
@@ -242,6 +243,9 @@ 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)

arch/x86/xen/enlighten_hvm.c

@@ -195,6 +195,8 @@ static void __init xen_hvm_guest_init(void)
 	if (xen_pv_domain())
 		return;
 
+	xen_set_restricted_virtio_memory_access();
+
 	init_hvm_pv_info();
 
 	reserve_shared_info();

arch/x86/xen/enlighten_pv.c

@@ -109,6 +109,8 @@ static DEFINE_PER_CPU(struct tls_descs, shadow_tls_desc);
 
 static void __init xen_pv_init_platform(void)
 {
+	xen_set_restricted_virtio_memory_access();
+
 	populate_extra_pte(fix_to_virt(FIX_PARAVIRT_BOOTMAP));
 
 	set_fixmap(FIX_PARAVIRT_BOOTMAP, xen_start_info->shared_info);

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

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 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");

drivers/xen/Kconfig

@@ -335,4 +335,24 @@ config XEN_UNPOPULATED_ALLOC
 	  having to balloon out RAM regions in order to obtain physical memory
 	  space to create such mappings.
 
+config XEN_GRANT_DMA_IOMMU
+	bool
+	select IOMMU_API
+
+config XEN_GRANT_DMA_OPS
+	bool
+	select DMA_OPS
+
+config XEN_VIRTIO
+	bool "Xen virtio support"
+	depends on VIRTIO
+	select XEN_GRANT_DMA_OPS
+	select XEN_GRANT_DMA_IOMMU if OF
+	help
+	  Enable virtio support for running as Xen guest. Depending on the
+	  guest type this will require special support on the backend side
+	  (qemu or kernel, depending on the virtio device types used).
+
+	  If in doubt, say n.
+
 endmenu

drivers/xen/Makefile

@@ -39,3 +39,5 @@ xen-gntalloc-y				:= gntalloc.o
 xen-privcmd-y				:= privcmd.o privcmd-buf.o
 obj-$(CONFIG_XEN_FRONT_PGDIR_SHBUF)	+= xen-front-pgdir-shbuf.o
 obj-$(CONFIG_XEN_UNPOPULATED_ALLOC)	+= unpopulated-alloc.o
+obj-$(CONFIG_XEN_GRANT_DMA_OPS)		+= grant-dma-ops.o
+obj-$(CONFIG_XEN_GRANT_DMA_IOMMU)	+= grant-dma-iommu.o

drivers/xen/grant-dma-iommu.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Stub IOMMU driver which does nothing.
+ * The main purpose of it being present is to reuse generic IOMMU device tree
+ * bindings by Xen grant DMA-mapping layer.
+ *
+ * Copyright (C) 2022 EPAM Systems Inc.
+ */
+
+#include <linux/iommu.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct grant_dma_iommu_device {
+	struct device *dev;
+	struct iommu_device iommu;
+};
+
+/* Nothing is really needed here */
+static const struct iommu_ops grant_dma_iommu_ops;
+
+static const struct of_device_id grant_dma_iommu_of_match[] = {
+	{ .compatible = "xen,grant-dma" },
+	{ },
+};
+
+static int grant_dma_iommu_probe(struct platform_device *pdev)
+{
+	struct grant_dma_iommu_device *mmu;
+	int ret;
+
+	mmu = devm_kzalloc(&pdev->dev, sizeof(*mmu), GFP_KERNEL);
+	if (!mmu)
+		return -ENOMEM;
+
+	mmu->dev = &pdev->dev;
+
+	ret = iommu_device_register(&mmu->iommu, &grant_dma_iommu_ops, &pdev->dev);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, mmu);
+
+	return 0;
+}
+
+static int grant_dma_iommu_remove(struct platform_device *pdev)
+{
+	struct grant_dma_iommu_device *mmu = platform_get_drvdata(pdev);
+
+	platform_set_drvdata(pdev, NULL);
+	iommu_device_unregister(&mmu->iommu);
+
+	return 0;
+}
+
+static struct platform_driver grant_dma_iommu_driver = {
+	.driver = {
+		.name = "grant-dma-iommu",
+		.of_match_table = grant_dma_iommu_of_match,
+	},
+	.probe = grant_dma_iommu_probe,
+	.remove = grant_dma_iommu_remove,
+};
+
+static int __init grant_dma_iommu_init(void)
+{
+	struct device_node *iommu_np;
+
+	iommu_np = of_find_matching_node(NULL, grant_dma_iommu_of_match);
+	if (!iommu_np)
+		return 0;
+
+	of_node_put(iommu_np);
+
+	return platform_driver_register(&grant_dma_iommu_driver);
+}
+subsys_initcall(grant_dma_iommu_init);

drivers/xen/grant-dma-ops.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Xen grant DMA-mapping layer - contains special DMA-mapping routines
+ * for providing grant references as DMA addresses to be used by frontends
+ * (e.g. virtio) in Xen guests
+ *
+ * Copyright (c) 2021, Juergen Gross <jgross@suse.com>
+ */
+
+#include <linux/module.h>
+#include <linux/dma-map-ops.h>
+#include <linux/of.h>
+#include <linux/pfn.h>
+#include <linux/xarray.h>
+#include <xen/xen.h>
+#include <xen/xen-ops.h>
+#include <xen/grant_table.h>
+
+struct xen_grant_dma_data {
+	/* The ID of backend domain */
+	domid_t backend_domid;
+	/* Is device behaving sane? */
+	bool broken;
+};
+
+static DEFINE_XARRAY(xen_grant_dma_devices);
+
+#define XEN_GRANT_DMA_ADDR_OFF	(1ULL << 63)
+
+static inline dma_addr_t grant_to_dma(grant_ref_t grant)
+{
+	return XEN_GRANT_DMA_ADDR_OFF | ((dma_addr_t)grant << PAGE_SHIFT);
+}
+
+static inline grant_ref_t dma_to_grant(dma_addr_t dma)
+{
+	return (grant_ref_t)((dma & ~XEN_GRANT_DMA_ADDR_OFF) >> PAGE_SHIFT);
+}
+
+static struct xen_grant_dma_data *find_xen_grant_dma_data(struct device *dev)
+{
+	struct xen_grant_dma_data *data;
+
+	xa_lock(&xen_grant_dma_devices);
+	data = xa_load(&xen_grant_dma_devices, (unsigned long)dev);
+	xa_unlock(&xen_grant_dma_devices);
+
+	return data;
+}
+
+/*
+ * DMA ops for Xen frontends (e.g. virtio).
+ *
+ * Used to act as a kind of software IOMMU for Xen guests by using grants as
+ * DMA addresses.
+ * Such a DMA address is formed by using the grant reference as a frame
+ * number and setting the highest address bit (this bit is for the backend
+ * to be able to distinguish it from e.g. a mmio address).
+ */
+static void *xen_grant_dma_alloc(struct device *dev, size_t size,
+				 dma_addr_t *dma_handle, gfp_t gfp,
+				 unsigned long attrs)
+{
+	struct xen_grant_dma_data *data;
+	unsigned int i, n_pages = PFN_UP(size);
+	unsigned long pfn;
+	grant_ref_t grant;
+	void *ret;
+
+	data = find_xen_grant_dma_data(dev);
+	if (!data)
+		return NULL;
+
+	if (unlikely(data->broken))
+		return NULL;
+
+	ret = alloc_pages_exact(n_pages * PAGE_SIZE, gfp);
+	if (!ret)
+		return NULL;
+
+	pfn = virt_to_pfn(ret);
+
+	if (gnttab_alloc_grant_reference_seq(n_pages, &grant)) {
+		free_pages_exact(ret, n_pages * PAGE_SIZE);
+		return NULL;
+	}
+
+	for (i = 0; i < n_pages; i++) {
+		gnttab_grant_foreign_access_ref(grant + i, data->backend_domid,
+				pfn_to_gfn(pfn + i), 0);
+	}
+
+	*dma_handle = grant_to_dma(grant);
+
+	return ret;
+}
+
+static void xen_grant_dma_free(struct device *dev, size_t size, void *vaddr,
+			       dma_addr_t dma_handle, unsigned long attrs)
+{
+	struct xen_grant_dma_data *data;
+	unsigned int i, n_pages = PFN_UP(size);
+	grant_ref_t grant;
+
+	data = find_xen_grant_dma_data(dev);
+	if (!data)
+		return;
+
+	if (unlikely(data->broken))
+		return;
+
+	grant = dma_to_grant(dma_handle);
+
+	for (i = 0; i < n_pages; i++) {
+		if (unlikely(!gnttab_end_foreign_access_ref(grant + i))) {
+			dev_alert(dev, "Grant still in use by backend domain, disabled for further use\n");
+			data->broken = true;
+			return;
+		}
+	}
+
+	gnttab_free_grant_reference_seq(grant, n_pages);
+
+	free_pages_exact(vaddr, n_pages * PAGE_SIZE);
+}
+
+static struct page *xen_grant_dma_alloc_pages(struct device *dev, size_t size,
+					      dma_addr_t *dma_handle,
+					      enum dma_data_direction dir,
+					      gfp_t gfp)
+{
+	void *vaddr;
+
+	vaddr = xen_grant_dma_alloc(dev, size, dma_handle, gfp, 0);
+	if (!vaddr)
+		return NULL;
+
+	return virt_to_page(vaddr);
+}
+
+static void xen_grant_dma_free_pages(struct device *dev, size_t size,
+				     struct page *vaddr, dma_addr_t dma_handle,
+				     enum dma_data_direction dir)
+{
+	xen_grant_dma_free(dev, size, page_to_virt(vaddr), dma_handle, 0);
+}
+
+static dma_addr_t xen_grant_dma_map_page(struct device *dev, struct page *page,
+					 unsigned long offset, size_t size,
+					 enum dma_data_direction dir,
+					 unsigned long attrs)
+{
+	struct xen_grant_dma_data *data;
+	unsigned int i, n_pages = PFN_UP(size);
+	grant_ref_t grant;
+	dma_addr_t dma_handle;
+
+	if (WARN_ON(dir == DMA_NONE))
+		return DMA_MAPPING_ERROR;
+
+	data = find_xen_grant_dma_data(dev);
+	if (!data)
+		return DMA_MAPPING_ERROR;
+
+	if (unlikely(data->broken))
+		return DMA_MAPPING_ERROR;
+
+	if (gnttab_alloc_grant_reference_seq(n_pages, &grant))
+		return DMA_MAPPING_ERROR;
+
+	for (i = 0; i < n_pages; i++) {
+		gnttab_grant_foreign_access_ref(grant + i, data->backend_domid,
+				xen_page_to_gfn(page) + i, dir == DMA_TO_DEVICE);
+	}
+
+	dma_handle = grant_to_dma(grant) + offset;
+
+	return dma_handle;
+}
+
+static void xen_grant_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
+				     size_t size, enum dma_data_direction dir,
+				     unsigned long attrs)
+{
+	struct xen_grant_dma_data *data;
+	unsigned int i, n_pages = PFN_UP(size);
+	grant_ref_t grant;
+
+	if (WARN_ON(dir == DMA_NONE))
+		return;
+
+	data = find_xen_grant_dma_data(dev);
+	if (!data)
+		return;
+
+	if (unlikely(data->broken))
+		return;
+
+	grant = dma_to_grant(dma_handle);
+
+	for (i = 0; i < n_pages; i++) {
+		if (unlikely(!gnttab_end_foreign_access_ref(grant + i))) {
+			dev_alert(dev, "Grant still in use by backend domain, disabled for further use\n");
+			data->broken = true;
+			return;
+		}
+	}
+
+	gnttab_free_grant_reference_seq(grant, n_pages);
+}
+
+static void xen_grant_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
+				   int nents, enum dma_data_direction dir,
+				   unsigned long attrs)
+{
+	struct scatterlist *s;
+	unsigned int i;
+
+	if (WARN_ON(dir == DMA_NONE))
+		return;
+
+	for_each_sg(sg, s, nents, i)
+		xen_grant_dma_unmap_page(dev, s->dma_address, sg_dma_len(s), dir,
+				attrs);
+}
+
+static int xen_grant_dma_map_sg(struct device *dev, struct scatterlist *sg,
+				int nents, enum dma_data_direction dir,
+				unsigned long attrs)
+{
+	struct scatterlist *s;
+	unsigned int i;
+
+	if (WARN_ON(dir == DMA_NONE))
+		return -EINVAL;
+
+	for_each_sg(sg, s, nents, i) {
+		s->dma_address = xen_grant_dma_map_page(dev, sg_page(s), s->offset,
+				s->length, dir, attrs);
+		if (s->dma_address == DMA_MAPPING_ERROR)
+			goto out;
+
+		sg_dma_len(s) = s->length;
+	}
+
+	return nents;
+
+out:
+	xen_grant_dma_unmap_sg(dev, sg, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
+	sg_dma_len(sg) = 0;
+
+	return -EIO;
+}
+
+static int xen_grant_dma_supported(struct device *dev, u64 mask)
+{
+	return mask == DMA_BIT_MASK(64);
+}
+
+static const struct dma_map_ops xen_grant_dma_ops = {
+	.alloc = xen_grant_dma_alloc,
+	.free = xen_grant_dma_free,
+	.alloc_pages = xen_grant_dma_alloc_pages,
+	.free_pages = xen_grant_dma_free_pages,
+	.mmap = dma_common_mmap,
+	.get_sgtable = dma_common_get_sgtable,
+	.map_page = xen_grant_dma_map_page,
+	.unmap_page = xen_grant_dma_unmap_page,
+	.map_sg = xen_grant_dma_map_sg,
+	.unmap_sg = xen_grant_dma_unmap_sg,
+	.dma_supported = xen_grant_dma_supported,
+};
+
+bool xen_is_grant_dma_device(struct device *dev)
+{
+	struct device_node *iommu_np;
+	bool has_iommu;
+
+	/* XXX Handle only DT devices for now */
+	if (!dev->of_node)
+		return false;
+
+	iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
+	has_iommu = iommu_np && of_device_is_compatible(iommu_np, "xen,grant-dma");
+	of_node_put(iommu_np);
+
+	return has_iommu;
+}
+
+void xen_grant_setup_dma_ops(struct device *dev)
+{
+	struct xen_grant_dma_data *data;
+	struct of_phandle_args iommu_spec;
+
+	data = find_xen_grant_dma_data(dev);
+	if (data) {
+		dev_err(dev, "Xen grant DMA data is already created\n");
+		return;
+	}
+
+	/* XXX ACPI device unsupported for now */
+	if (!dev->of_node)
+		goto err;
+
+	if (of_parse_phandle_with_args(dev->of_node, "iommus", "#iommu-cells",
+			0, &iommu_spec)) {
+		dev_err(dev, "Cannot parse iommus property\n");
+		goto err;
+	}
+
+	if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") ||
+			iommu_spec.args_count != 1) {
+		dev_err(dev, "Incompatible IOMMU node\n");
+		of_node_put(iommu_spec.np);
+		goto err;
+	}
+
+	of_node_put(iommu_spec.np);
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		goto err;
+
+	/*
+	 * The endpoint ID here means the ID of the domain where the corresponding
+	 * backend is running
+	 */
+	data->backend_domid = iommu_spec.args[0];
+
+	if (xa_err(xa_store(&xen_grant_dma_devices, (unsigned long)dev, data,
+			GFP_KERNEL))) {
+		dev_err(dev, "Cannot store Xen grant DMA data\n");
+		goto err;
+	}
+
+	dev->dma_ops = &xen_grant_dma_ops;
+
+	return;
+
+err:
+	dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
+}
+
+MODULE_DESCRIPTION("Xen grant DMA-mapping layer");
+MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
+MODULE_LICENSE("GPL");

drivers/xen/xlate_mmu.c

@@ -261,7 +261,6 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt,
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(xen_xlate_map_ballooned_pages);
 
 struct remap_pfn {
 	struct mm_struct *mm;

include/asm-generic/Kbuild

@@ -44,6 +44,7 @@ mandatory-y += msi.h
 mandatory-y += pci.h
 mandatory-y += percpu.h
 mandatory-y += pgalloc.h
+mandatory-y += platform-feature.h
 mandatory-y += preempt.h
 mandatory-y += rwonce.h
 mandatory-y += sections.h

include/asm-generic/platform-feature.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_PLATFORM_FEATURE_H
+#define _ASM_GENERIC_PLATFORM_FEATURE_H
+
+/* Number of arch specific feature flags. */
+#define PLATFORM_ARCH_FEAT_N	0
+
+#endif /* _ASM_GENERIC_PLATFORM_FEATURE_H */

include/linux/platform-feature.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PLATFORM_FEATURE_H
+#define _PLATFORM_FEATURE_H
+
+#include <linux/bitops.h>
+#include <asm/platform-feature.h>
+
+/* The platform features are starting with the architecture specific ones. */
+
+/* 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);
+bool platform_has(unsigned int feature);
+
+#endif /* _PLATFORM_FEATURE_H */

include/linux/virtio_config.h

@@ -604,13 +604,4 @@ 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 */

include/xen/arm/xen-ops.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARM_XEN_OPS_H
+#define _ASM_ARM_XEN_OPS_H
+
+#include <xen/swiotlb-xen.h>
+#include <xen/xen-ops.h>
+
+static inline void xen_setup_dma_ops(struct device *dev)
+{
+#ifdef CONFIG_XEN
+	if (xen_is_grant_dma_device(dev))
+		xen_grant_setup_dma_ops(dev);
+	else if (xen_swiotlb_detect())
+		dev->dma_ops = &xen_swiotlb_dma_ops;
+#endif
+}
+
+#endif /* _ASM_ARM_XEN_OPS_H */

include/xen/grant_table.h

@@ -127,10 +127,14 @@ int gnttab_try_end_foreign_access(grant_ref_t ref);
  */
 int gnttab_alloc_grant_references(u16 count, grant_ref_t *pprivate_head);
 
+int gnttab_alloc_grant_reference_seq(unsigned int count, grant_ref_t *first);
+
 void gnttab_free_grant_reference(grant_ref_t ref);
 
 void gnttab_free_grant_references(grant_ref_t head);
 
+void gnttab_free_grant_reference_seq(grant_ref_t head, unsigned int count);
+
 int gnttab_empty_grant_references(const grant_ref_t *pprivate_head);
 
 int gnttab_claim_grant_reference(grant_ref_t *pprivate_head);

include/xen/xen-ops.h

@@ -214,4 +214,17 @@ static inline void xen_preemptible_hcall_end(void) { }
 
 #endif /* CONFIG_XEN_PV && !CONFIG_PREEMPTION */
 
+#ifdef CONFIG_XEN_GRANT_DMA_OPS
+void xen_grant_setup_dma_ops(struct device *dev);
+bool xen_is_grant_dma_device(struct device *dev);
+#else
+static inline void xen_grant_setup_dma_ops(struct device *dev)
+{
+}
+static inline bool xen_is_grant_dma_device(struct device *dev)
+{
+	return false;
+}
+#endif /* CONFIG_XEN_GRANT_DMA_OPS */
+
 #endif /* INCLUDE_XEN_OPS_H */

include/xen/xen.h

@@ -52,6 +52,14 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
 extern u64 xen_saved_max_mem_size;
 #endif
 
+#include <linux/platform-feature.h>
+
+static inline void xen_set_restricted_virtio_memory_access(void)
+{
+	if (IS_ENABLED(CONFIG_XEN_VIRTIO) && xen_domain())
+		platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
+}
+
 #ifdef CONFIG_XEN_UNPOPULATED_ALLOC
 int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages);
 void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages);

kernel/Makefile

@@ -7,7 +7,7 @@ obj-y     = fork.o exec_domain.o panic.o \
 	    cpu.o exit.o softirq.o resource.o \
 	    sysctl.o capability.o ptrace.o user.o \
 	    signal.o sys.o umh.o workqueue.o pid.o task_work.o \
-	    extable.o params.o \
+	    extable.o params.o platform-feature.o \
 	    kthread.o sys_ni.o nsproxy.o \
 	    notifier.o ksysfs.o cred.o reboot.o \
 	    async.o range.o smpboot.o ucount.o regset.o

kernel/platform-feature.c

+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bitops.h>
+#include <linux/cache.h>
+#include <linux/export.h>
+#include <linux/platform-feature.h>
+
+#define PLATFORM_FEAT_ARRAY_SZ  BITS_TO_LONGS(PLATFORM_FEAT_N)
+static unsigned long __read_mostly platform_features[PLATFORM_FEAT_ARRAY_SZ];
+
+void platform_set(unsigned int feature)
+{
+	set_bit(feature, platform_features);
+}
+EXPORT_SYMBOL_GPL(platform_set);
+
+void platform_clear(unsigned int feature)
+{
+	clear_bit(feature, platform_features);
+}
+EXPORT_SYMBOL_GPL(platform_clear);
+
+bool platform_has(unsigned int feature)
+{
+	return test_bit(feature, platform_features);
+}
+EXPORT_SYMBOL_GPL(platform_has);