iommu: Add virtio-iommu driver

The virtio IOMMU is a para-virtualized device, allowing to send IOMMU
requests such as map/unmap over virtio transport without emulating page
tables. This implementation handles ATTACH, DETACH, MAP and UNMAP
requests.

The bulk of the code transforms calls coming from the IOMMU API into
corresponding virtio requests. Mappings are kept in an interval tree
instead of page tables. A little more work is required for modular and x86
support, so for the moment the driver depends on CONFIG_VIRTIO=y and
CONFIG_ARM64.
Tested-by: Bharat Bhushan <bharat.bhushan@nxp.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

MAINTAINERS

@@ -16807,6 +16807,13 @@ S:	Maintained
 F:	drivers/virtio/virtio_input.c
 F:	include/uapi/linux/virtio_input.h
 
+VIRTIO IOMMU DRIVER
+M:	Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
+L:	virtualization@lists.linux-foundation.org
+S:	Maintained
+F:	drivers/iommu/virtio-iommu.c
+F:	include/uapi/linux/virtio_iommu.h
+
 VIRTUAL BOX GUEST DEVICE DRIVER
 M:	Hans de Goede <hdegoede@redhat.com>
 M:	Arnd Bergmann <arnd@arndb.de>

drivers/iommu/Kconfig

@@ -473,4 +473,15 @@ config HYPERV_IOMMU
 	  Stub IOMMU driver to handle IRQs as to allow Hyper-V Linux
 	  guests to run with x2APIC mode enabled.
 
+config VIRTIO_IOMMU
+	bool "Virtio IOMMU driver"
+	depends on VIRTIO=y
+	depends on ARM64
+	select IOMMU_API
+	select INTERVAL_TREE
+	help
+	  Para-virtualised IOMMU driver with virtio.
+
+	  Say Y here if you intend to run this kernel as a guest.
+
 endif # IOMMU_SUPPORT

drivers/iommu/Makefile

@@ -33,3 +33,4 @@ obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
 obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
 obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o
 obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
+obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o

include/uapi/linux/virtio_ids.h

@@ -43,5 +43,6 @@
 #define VIRTIO_ID_INPUT        18 /* virtio input */
 #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
 #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
+#define VIRTIO_ID_IOMMU        23 /* virtio IOMMU */
 
 #endif /* _LINUX_VIRTIO_IDS_H */

include/uapi/linux/virtio_iommu.h

+/* SPDX-License-Identifier: BSD-3-Clause */
+/*
+ * Virtio-iommu definition v0.9
+ *
+ * Copyright (C) 2018 Arm Ltd.
+ */
+#ifndef _UAPI_LINUX_VIRTIO_IOMMU_H
+#define _UAPI_LINUX_VIRTIO_IOMMU_H
+
+#include <linux/types.h>
+
+/* Feature bits */
+#define VIRTIO_IOMMU_F_INPUT_RANGE		0
+#define VIRTIO_IOMMU_F_DOMAIN_BITS		1
+#define VIRTIO_IOMMU_F_MAP_UNMAP		2
+#define VIRTIO_IOMMU_F_BYPASS			3
+
+struct virtio_iommu_range {
+	__u64					start;
+	__u64					end;
+};
+
+struct virtio_iommu_config {
+	/* Supported page sizes */
+	__u64					page_size_mask;
+	/* Supported IOVA range */
+	struct virtio_iommu_range		input_range;
+	/* Max domain ID size */
+	__u8					domain_bits;
+	__u8					padding[3];
+	/* Probe buffer size */
+	__u32					probe_size;
+};
+
+/* Request types */
+#define VIRTIO_IOMMU_T_ATTACH			0x01
+#define VIRTIO_IOMMU_T_DETACH			0x02
+#define VIRTIO_IOMMU_T_MAP			0x03
+#define VIRTIO_IOMMU_T_UNMAP			0x04
+
+/* Status types */
+#define VIRTIO_IOMMU_S_OK			0x00
+#define VIRTIO_IOMMU_S_IOERR			0x01
+#define VIRTIO_IOMMU_S_UNSUPP			0x02
+#define VIRTIO_IOMMU_S_DEVERR			0x03
+#define VIRTIO_IOMMU_S_INVAL			0x04
+#define VIRTIO_IOMMU_S_RANGE			0x05
+#define VIRTIO_IOMMU_S_NOENT			0x06
+#define VIRTIO_IOMMU_S_FAULT			0x07
+
+struct virtio_iommu_req_head {
+	__u8					type;
+	__u8					reserved[3];
+};
+
+struct virtio_iommu_req_tail {
+	__u8					status;
+	__u8					reserved[3];
+};
+
+struct virtio_iommu_req_attach {
+	struct virtio_iommu_req_head		head;
+	__le32					domain;
+	__le32					endpoint;
+	__u8					reserved[8];
+	struct virtio_iommu_req_tail		tail;
+};
+
+struct virtio_iommu_req_detach {
+	struct virtio_iommu_req_head		head;
+	__le32					domain;
+	__le32					endpoint;
+	__u8					reserved[8];
+	struct virtio_iommu_req_tail		tail;
+};
+
+#define VIRTIO_IOMMU_MAP_F_READ			(1 << 0)
+#define VIRTIO_IOMMU_MAP_F_WRITE		(1 << 1)
+#define VIRTIO_IOMMU_MAP_F_EXEC			(1 << 2)
+#define VIRTIO_IOMMU_MAP_F_MMIO			(1 << 3)
+
+#define VIRTIO_IOMMU_MAP_F_MASK			(VIRTIO_IOMMU_MAP_F_READ |	\
+						 VIRTIO_IOMMU_MAP_F_WRITE |	\
+						 VIRTIO_IOMMU_MAP_F_EXEC |	\
+						 VIRTIO_IOMMU_MAP_F_MMIO)
+
+struct virtio_iommu_req_map {
+	struct virtio_iommu_req_head		head;
+	__le32					domain;
+	__le64					virt_start;
+	__le64					virt_end;
+	__le64					phys_start;
+	__le32					flags;
+	struct virtio_iommu_req_tail		tail;
+};
+
+struct virtio_iommu_req_unmap {
+	struct virtio_iommu_req_head		head;
+	__le32					domain;
+	__le64					virt_start;
+	__le64					virt_end;
+	__u8					reserved[4];
+	struct virtio_iommu_req_tail		tail;
+};
+
+#endif