[RFC 04/13] vfio: introduce vfio-cxl core preludes

[Zhi Wang <zhiw@nvidia.com>]

In VFIO, common functions that used by VFIO variant drivers are managed
in a set of "core" functions. E.g. the vfio-pci-core provides the common
functions used by VFIO variant drviers to support PCI device
passhthrough.

Although the CXL type-2 device has a PCI-compatible interface for device
configuration and programming, they still needs special handlings when
initialize the device:

- Probing the CXL DVSECs in the configuration.
- Probing the CXL register groups implemented by the device.
- Configuring the CXL device state required by the kernel CXL core.
- Create the CXL region.
- Special handlings of the CXL MMIO BAR.

Introduce vfio-cxl core predules to hold all the common functions used
by VFIO variant drivers to support CXL device passthrough.

Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 drivers/vfio/pci/Kconfig         |   4 +
 drivers/vfio/pci/Makefile        |   3 +
 drivers/vfio/pci/vfio_cxl_core.c | 264 +++++++++++++++++++++++++++++++
 include/linux/vfio_pci_core.h    |  37 +++++
 4 files changed, 308 insertions(+)
 create mode 100644 drivers/vfio/pci/vfio_cxl_core.c

diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index bf50ffa10bde..2196e79b132b 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -7,6 +7,10 @@ config VFIO_PCI_CORE
 	select VFIO_VIRQFD
 	select IRQ_BYPASS_MANAGER
 
+config VFIO_CXL_CORE
+	tristate
+	select VFIO_PCI_CORE
+
 config VFIO_PCI_MMAP
 	def_bool y if !S390
 	depends on VFIO_PCI_CORE
diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
index cf00c0a7e55c..b51221b94b0b 100644
--- a/drivers/vfio/pci/Makefile
+++ b/drivers/vfio/pci/Makefile
@@ -8,6 +8,9 @@ vfio-pci-y := vfio_pci.o
 vfio-pci-$(CONFIG_VFIO_PCI_IGD) += vfio_pci_igd.o
 obj-$(CONFIG_VFIO_PCI) += vfio-pci.o
 
+vfio-cxl-core-y := vfio_cxl_core.o
+obj-$(CONFIG_VFIO_CXL_CORE) += vfio-cxl-core.o
+
 obj-$(CONFIG_MLX5_VFIO_PCI)           += mlx5/
 
 obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/
diff --git a/drivers/vfio/pci/vfio_cxl_core.c b/drivers/vfio/pci/vfio_cxl_core.c
new file mode 100644
index 000000000000..6a7859333f67
--- /dev/null
+++ b/drivers/vfio/pci/vfio_cxl_core.c
@@ -0,0 +1,264 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES. All rights reserved
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/device.h>
+#include <linux/eventfd.h>
+#include <linux/file.h>
+#include <linux/interrupt.h>
+#include <linux/iommu.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/notifier.h>
+#include <linux/pci.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+
+#include "vfio_pci_priv.h"
+
+#define DRIVER_AUTHOR "Zhi Wang <zhiw@nvidia.com>"
+#define DRIVER_DESC "core driver for VFIO based CXL devices"
+
+static int get_hpa_and_request_dpa(struct vfio_pci_core_device *core_dev)
+{
+	struct vfio_cxl *cxl = &core_dev->cxl;
+	struct pci_dev *pdev = core_dev->pdev;
+	u64 max;
+
+	cxl->cxlrd = cxl_get_hpa_freespace(cxl->endpoint, 1,
+					   CXL_DECODER_F_RAM |
+					   CXL_DECODER_F_TYPE2,
+					   &max);
+	if (IS_ERR(cxl->cxlrd)) {
+		pci_err(pdev, "Fail to get HPA space.\n");
+		return PTR_ERR(cxl->cxlrd);
+	}
+
+	if (max < cxl->region.size) {
+		pci_err(pdev, "No enough free HPA space %llu < %llu\n",
+			max, cxl->region.size);
+		return -ENOSPC;
+	}
+
+	cxl->cxled = cxl_request_dpa(cxl->endpoint, true, cxl->region.size,
+				     cxl->region.size);
+	if (IS_ERR(cxl->cxled)) {
+		pci_err(pdev, "Fail to request DPA\n");
+		return PTR_ERR(cxl->cxled);
+	}
+
+	return 0;
+}
+
+static int create_cxl_region(struct vfio_pci_core_device *core_dev)
+{
+	struct vfio_cxl *cxl = &core_dev->cxl;
+	struct pci_dev *pdev = core_dev->pdev;
+	resource_size_t start, end;
+	int ret;
+
+	ret = cxl_accel_request_resource(cxl->cxlds, true);
+	if (ret) {
+		pci_err(pdev, "Fail to request CXL resource\n");
+		return ret;
+	}
+
+	if (!cxl_await_media_ready(cxl->cxlds)) {
+		cxl_accel_set_media_ready(cxl->cxlds);
+	} else {
+		pci_err(pdev, "CXL media is not active\n");
+		return ret;
+	}
+
+	cxl->cxlmd = devm_cxl_add_memdev(&pdev->dev, cxl->cxlds);
+	if (IS_ERR(cxl->cxlmd)) {
+		pci_err(pdev, "Fail to create CXL memdev\n");
+		return PTR_ERR(cxl->cxlmd);
+	}
+
+	cxl->endpoint = cxl_acquire_endpoint(cxl->cxlmd);
+	if (IS_ERR(cxl->endpoint)) {
+		pci_err(pdev, "Fail to acquire CXL endpoint\n");
+		return PTR_ERR(cxl->endpoint);
+	}
+
+	ret = get_hpa_and_request_dpa(core_dev);
+	if (ret)
+		goto out;
+
+	cxl->region.region = cxl_create_region(cxl->cxlrd, &cxl->cxled, 1);
+	if (IS_ERR(cxl->region.region)) {
+		ret = PTR_ERR(cxl->region.region);
+		pci_err(pdev, "Fail to create CXL region\n");
+		cxl_dpa_free(cxl->cxled);
+		goto out;
+	}
+
+	cxl_accel_get_region_params(cxl->region.region, &start, &end);
+
+	cxl->region.addr = start;
+out:
+	cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);
+	return ret;
+}
+
+/* Standard CXL-type 2 driver initialization sequence */
+static int enable_cxl(struct vfio_pci_core_device *core_dev, u16 dvsec)
+{
+	struct vfio_cxl *cxl = &core_dev->cxl;
+	struct pci_dev *pdev = core_dev->pdev;
+	u32 count;
+	u64 offset, size;
+	int ret;
+
+	cxl->cxlds = cxl_accel_state_create(&pdev->dev, cxl->caps);
+	if (IS_ERR(cxl->cxlds))
+		return PTR_ERR(cxl->cxlds);
+
+	cxl_accel_set_dvsec(cxl->cxlds, dvsec);
+	cxl_accel_set_serial(cxl->cxlds, pdev->dev.id);
+
+	cxl_accel_set_resource(cxl->cxlds, cxl->dpa_res, CXL_ACCEL_RES_DPA);
+	cxl_accel_set_resource(cxl->cxlds, cxl->ram_res, CXL_ACCEL_RES_RAM);
+
+	ret = cxl_pci_accel_setup_regs(pdev, cxl->cxlds);
+	if (ret) {
+		pci_err(pdev, "Fail to setup CXL accel regs\n");
+		return ret;
+	}
+
+	ret = cxl_get_hdm_info(cxl->cxlds, &count, &offset, &size);
+	if (ret)
+		return ret;
+
+	if (!count || !size) {
+		pci_err(pdev, "Fail to find CXL HDM reg offset\n");
+		return -ENODEV;
+	}
+
+	cxl->hdm_count = count;
+	cxl->hdm_reg_offset = offset;
+	cxl->hdm_reg_size = size;
+
+	return create_cxl_region(core_dev);
+}
+
+static void disable_cxl(struct vfio_pci_core_device *core_dev)
+{
+	struct vfio_cxl *cxl = &core_dev->cxl;
+
+	if (cxl->region.region)
+		cxl_region_detach(cxl->cxled);
+
+	if (cxl->cxled)
+		cxl_dpa_free(cxl->cxled);
+}
+
+int vfio_cxl_core_enable(struct vfio_pci_core_device *core_dev)
+{
+	struct vfio_cxl *cxl = &core_dev->cxl;
+	struct pci_dev *pdev = core_dev->pdev;
+	u16 dvsec;
+	int ret;
+
+	dvsec = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL,
+					  CXL_DVSEC_PCIE_DEVICE);
+	if (!dvsec)
+		return -ENODEV;
+
+	if (!cxl->region.size)
+		return -EINVAL;
+
+	ret = vfio_pci_core_enable(core_dev);
+	if (ret)
+		return ret;
+
+	ret = enable_cxl(core_dev, dvsec);
+	if (ret)
+		goto err_enable_cxl_device;
+
+	return 0;
+
+err_enable_cxl_device:
+	vfio_pci_core_disable(core_dev);
+	return ret;
+}
+EXPORT_SYMBOL(vfio_cxl_core_enable);
+
+void vfio_cxl_core_finish_enable(struct vfio_pci_core_device *core_dev)
+{
+	vfio_pci_core_finish_enable(core_dev);
+}
+EXPORT_SYMBOL(vfio_cxl_core_finish_enable);
+
+void vfio_cxl_core_close_device(struct vfio_device *vdev)
+{
+	struct vfio_pci_core_device *core_dev =
+		container_of(vdev, struct vfio_pci_core_device, vdev);
+
+	disable_cxl(core_dev);
+	vfio_pci_core_close_device(vdev);
+}
+EXPORT_SYMBOL(vfio_cxl_core_close_device);
+
+/*
+ * Configure the resource required by the kernel CXL core:
+ * device DPA and device RAM size
+ */
+void vfio_cxl_core_set_resource(struct vfio_pci_core_device *core_dev,
+				struct resource res,
+				enum accel_resource type)
+{
+	struct vfio_cxl *cxl = &core_dev->cxl;
+
+	switch (type) {
+	case CXL_ACCEL_RES_DPA:
+		cxl->dpa_size = res.end - res.start + 1;
+		cxl->dpa_res = res;
+		break;
+
+	case CXL_ACCEL_RES_RAM:
+		cxl->ram_res = res;
+		break;
+
+	default:
+		WARN(1, "invalid resource type: %d\n", type);
+		break;
+	}
+}
+EXPORT_SYMBOL(vfio_cxl_core_set_resource);
+
+/* Configure the expected CXL region size to be created */
+void vfio_cxl_core_set_region_size(struct vfio_pci_core_device *core_dev,
+				   u64 size)
+{
+	struct vfio_cxl *cxl = &core_dev->cxl;
+
+	if (WARN_ON(size > cxl->dpa_size))
+		return;
+
+	if (WARN_ON(cxl->region.region))
+		return;
+
+	cxl->region.size = size;
+}
+EXPORT_SYMBOL(vfio_cxl_core_set_region_size);
+
+/* Configure the driver cap required by the kernel CXL core */
+void vfio_cxl_core_set_driver_hdm_cap(struct vfio_pci_core_device *core_dev)
+{
+	struct vfio_cxl *cxl = &core_dev->cxl;
+
+	cxl->caps |= CXL_ACCEL_DRIVER_CAP_HDM;
+}
+EXPORT_SYMBOL(vfio_cxl_core_set_driver_hdm_cap);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_IMPORT_NS(CXL);
diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index fbb472dd99b3..7762d4a3e825 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -15,6 +15,8 @@
 #include <linux/types.h>
 #include <linux/uuid.h>
 #include <linux/notifier.h>
+#include <linux/cxl_accel_mem.h>
+#include <linux/cxl_accel_pci.h>
 
 #ifndef VFIO_PCI_CORE_H
 #define VFIO_PCI_CORE_H
@@ -49,6 +51,31 @@ struct vfio_pci_region {
 	u32				flags;
 };
 
+struct vfio_cxl_region {
+	u64 size;
+	u64 addr;
+	struct cxl_region *region;
+};
+
+struct vfio_cxl {
+	u8 caps;
+	u64 dpa_size;
+
+	u32 hdm_count;
+	u64 hdm_reg_offset;
+	u64 hdm_reg_size;
+
+	struct cxl_dev_state *cxlds;
+	struct cxl_memdev *cxlmd;
+	struct cxl_root_decoder *cxlrd;
+	struct cxl_port *endpoint;
+	struct cxl_endpoint_decoder *cxled;
+	struct resource dpa_res;
+	struct resource ram_res;
+
+	struct vfio_cxl_region region;
+};
+
 struct vfio_pci_core_device {
 	struct vfio_device	vdev;
 	struct pci_dev		*pdev;
@@ -94,6 +121,7 @@ struct vfio_pci_core_device {
 	struct vfio_pci_core_device	*sriov_pf_core_dev;
 	struct notifier_block	nb;
 	struct rw_semaphore	memory_lock;
+	struct vfio_cxl		cxl;
 };
 
 /* Will be exported for vfio pci drivers usage */
@@ -159,4 +187,13 @@ VFIO_IOREAD_DECLARATION(32)
 VFIO_IOREAD_DECLARATION(64)
 #endif
 
+int vfio_cxl_core_enable(struct vfio_pci_core_device *core_dev);
+void vfio_cxl_core_finish_enable(struct vfio_pci_core_device *core_dev);
+void vfio_cxl_core_close_device(struct vfio_device *vdev);
+void vfio_cxl_core_set_resource(struct vfio_pci_core_device *core_dev,
+				struct resource res,
+				enum accel_resource type);
+void vfio_cxl_core_set_region_size(struct vfio_pci_core_device *core_dev,
+				   u64 size);
+void vfio_cxl_core_set_driver_hdm_cap(struct vfio_pci_core_device *core_dev);
 #endif /* VFIO_PCI_CORE_H */
-- 
2.34.1