On Fri, 16 Feb 2024 08:31:28 +0530
[off-list ref] wrote:

Let's keep the header inclusion in an alphabet order.

With that addressed,

Reviewed-by: Zhi Wang <zhi.wang.linux@gmail.com>

+/*
+ * The device memory usable to the workloads running in the VM is
cached
+ * and showcased as a 64b device BAR (comprising of BAR4 and BAR5
region)
+ * to the VM and is represented as usemem.
+ * Moreover, the VM GPU device driver needs a non-cacheable region to
+ * support the MIG feature. This region is also exposed as a 64b BAR
+ * (comprising of BAR2 and BAR3 region) and represented as resmem.
+ */
+#define RESMEM_REGION_INDEX VFIO_PCI_BAR2_REGION_INDEX
+#define USEMEM_REGION_INDEX VFIO_PCI_BAR4_REGION_INDEX
+
+/* Memory size expected as non cached and reserved by the VM driver
*/ +#define RESMEM_SIZE SZ_1G
+
+/* A hardwired and constant ABI value between the GPU FW and VFIO
driver. */ +#define MEMBLK_SIZE SZ_512M
+
+/*
+ * The state of the two device memory region - resmem and usemem - is
+ * saved as struct mem_region.
+ */
+struct mem_region {
+	phys_addr_t memphys;    /* Base physical address of the
region */
+	size_t memlength;       /* Region size */
+	size_t bar_size;        /* Reported region BAR size */
+	__le64 bar_val;         /* Emulated BAR offset registers */
+	union {
+		void *memaddr;
+		void __iomem *ioaddr;
+	};                      /* Base virtual address of the
region */ +};
+
+struct nvgrace_gpu_pci_core_device {
+	struct vfio_pci_core_device core_device;
+	/* Cached and usable memory for the VM. */
+	struct mem_region usemem;
+	/* Non cached memory carved out from the end of device
memory */
+	struct mem_region resmem;
+	/* Lock to control device memory kernel mapping */
+	struct mutex remap_lock;
+};
+
+static void nvgrace_gpu_init_fake_bar_emu_regs(struct vfio_device
*core_vdev) +{
+	struct nvgrace_gpu_pci_core_device *nvdev =
+		container_of(core_vdev, struct
nvgrace_gpu_pci_core_device,
+			     core_device.vdev);
+
+	nvdev->resmem.bar_val = 0;
+	nvdev->usemem.bar_val = 0;
+}
+
+/* Choose the structure corresponding to the fake BAR with a given
index. */ +static struct mem_region *
+nvgrace_gpu_memregion(int index,
+		      struct nvgrace_gpu_pci_core_device *nvdev)
+{
+	if (index == USEMEM_REGION_INDEX)
+		return &nvdev->usemem;
+
+	if (index == RESMEM_REGION_INDEX)
+		return &nvdev->resmem;
+
+	return NULL;
+}
+
+static int nvgrace_gpu_open_device(struct vfio_device *core_vdev)
+{
+	struct vfio_pci_core_device *vdev =
+		container_of(core_vdev, struct vfio_pci_core_device,
vdev);
+	struct nvgrace_gpu_pci_core_device *nvdev =
+		container_of(core_vdev, struct
nvgrace_gpu_pci_core_device,
+			     core_device.vdev);
+	int ret;
+
+	ret = vfio_pci_core_enable(vdev);
+	if (ret)
+		return ret;
+
+	if (nvdev->usemem.memlength) {
+		nvgrace_gpu_init_fake_bar_emu_regs(core_vdev);
+		mutex_init(&nvdev->remap_lock);
+	}
+
+	vfio_pci_core_finish_enable(vdev);
+
+	return 0;
+}
+
+static void nvgrace_gpu_close_device(struct vfio_device *core_vdev)
+{
+	struct nvgrace_gpu_pci_core_device *nvdev =
+		container_of(core_vdev, struct
nvgrace_gpu_pci_core_device,
+			     core_device.vdev);
+
+	/* Unmap the mapping to the device memory cached region */
+	if (nvdev->usemem.memaddr) {
+		memunmap(nvdev->usemem.memaddr);
+		nvdev->usemem.memaddr = NULL;
+	}
+
+	/* Unmap the mapping to the device memory non-cached region
*/
+	if (nvdev->resmem.ioaddr) {
+		iounmap(nvdev->resmem.ioaddr);
+		nvdev->resmem.ioaddr = NULL;
+	}
+
+	mutex_destroy(&nvdev->remap_lock);
+
+	vfio_pci_core_close_device(core_vdev);
+}
+
+static int nvgrace_gpu_mmap(struct vfio_device *core_vdev,
+			    struct vm_area_struct *vma)
+{
+	struct nvgrace_gpu_pci_core_device *nvdev =
+		container_of(core_vdev, struct
nvgrace_gpu_pci_core_device,
+			     core_device.vdev);
+
+	struct mem_region *memregion;
+	unsigned long start_pfn;
+	u64 req_len, pgoff, end;
+	unsigned int index;
+	int ret = 0;
+
+	index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT -
PAGE_SHIFT); +
+	memregion = nvgrace_gpu_memregion(index, nvdev);
+	if (!memregion)
+		return vfio_pci_core_mmap(core_vdev, vma);
+
+	/*
+	 * Request to mmap the BAR. Map to the CPU accessible memory
on the
+	 * GPU using the memory information gathered from the system
ACPI
+	 * tables.
+	 */
+	pgoff = vma->vm_pgoff &
+		((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
+
+	if (check_sub_overflow(vma->vm_end, vma->vm_start, &req_len)
||
+	    check_add_overflow(PHYS_PFN(memregion->memphys), pgoff,
&start_pfn) ||
+	    check_add_overflow(PFN_PHYS(pgoff), req_len, &end))
+		return -EOVERFLOW;
+
+	/*
+	 * Check that the mapping request does not go beyond
available device
+	 * memory size
+	 */
+	if (end > memregion->memlength)
+		return -EINVAL;
+
+	/*
+	 * The carved out region of the device memory needs the
NORMAL_NC
+	 * property. Communicate as such to the hypervisor.
+	 */
+	if (index == RESMEM_REGION_INDEX)
+		vma->vm_page_prot =
pgprot_writecombine(vma->vm_page_prot); +
+	/*
+	 * Perform a PFN map to the memory and back the device BAR
by the
+	 * GPU memory.
+	 *
+	 * The available GPU memory size may not be power-of-2
aligned. The
+	 * remainder is only backed by vfio_device_ops read/write
handlers.
+	 *
+	 * During device reset, the GPU is safely disconnected to
the CPU
+	 * and access to the BAR will be immediately returned
preventing
+	 * machine check.
+	 */
+	ret = remap_pfn_range(vma, vma->vm_start, start_pfn,
+			      req_len, vma->vm_page_prot);
+	if (ret)
+		return ret;
+
+	vma->vm_pgoff = start_pfn;
+
+	return 0;
+}
+
+static long
+nvgrace_gpu_ioctl_get_region_info(struct vfio_device *core_vdev,
+				  unsigned long arg)
+{
+	struct nvgrace_gpu_pci_core_device *nvdev =
+		container_of(core_vdev, struct
nvgrace_gpu_pci_core_device,
+			     core_device.vdev);
+	unsigned long minsz = offsetofend(struct vfio_region_info,
offset);
+	struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
+	struct vfio_region_info_cap_sparse_mmap *sparse;
+	struct vfio_region_info info;
+	struct mem_region *memregion;
+	u32 size;
+	int ret;
+
+	if (copy_from_user(&info, (void __user *)arg, minsz))
+		return -EFAULT;
+
+	if (info.argsz < minsz)
+		return -EINVAL;
+
+	/*
+	 * Request to determine the BAR region information. Send the
+	 * GPU memory information.
+	 */
+	memregion = nvgrace_gpu_memregion(info.index, nvdev);
+	if (!memregion)
+		return vfio_pci_core_ioctl(core_vdev,
+
VFIO_DEVICE_GET_REGION_INFO, arg); +
+	size = struct_size(sparse, areas, 1);
+
+	/*
+	 * Setup for sparse mapping for the device memory. Only the
+	 * available device memory on the hardware is shown as a
+	 * mappable region.
+	 */
+	sparse = kzalloc(size, GFP_KERNEL);
+	if (!sparse)
+		return -ENOMEM;
+
+	sparse->nr_areas = 1;
+	sparse->areas[0].offset = 0;
+	sparse->areas[0].size = memregion->memlength;
+	sparse->header.id = VFIO_REGION_INFO_CAP_SPARSE_MMAP;
+	sparse->header.version = 1;
+
+	ret = vfio_info_add_capability(&caps, &sparse->header, size);
+	kfree(sparse);
+	if (ret)
+		return ret;
+
+	info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
+	/*
+	 * The region memory size may not be power-of-2 aligned.
+	 * Given that the memory  as a BAR and may not be
+	 * aligned, roundup to the next power-of-2.
+	 */
+	info.size = memregion->bar_size;
+	info.flags = VFIO_REGION_INFO_FLAG_READ |
+		     VFIO_REGION_INFO_FLAG_WRITE |
+		     VFIO_REGION_INFO_FLAG_MMAP;
+
+	if (caps.size) {
+		info.flags |= VFIO_REGION_INFO_FLAG_CAPS;
+		if (info.argsz < sizeof(info) + caps.size) {
+			info.argsz = sizeof(info) + caps.size;
+			info.cap_offset = 0;
+		} else {
+			vfio_info_cap_shift(&caps, sizeof(info));
+			if (copy_to_user((void __user *)arg +
+					 sizeof(info), caps.buf,
+					 caps.size)) {
+				kfree(caps.buf);
+				return -EFAULT;
+			}
+			info.cap_offset = sizeof(info);
+		}
+		kfree(caps.buf);
+	}
+	return copy_to_user((void __user *)arg, &info, minsz) ?
+			    -EFAULT : 0;
+}
+
+static long nvgrace_gpu_ioctl(struct vfio_device *core_vdev,
+			      unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	case VFIO_DEVICE_GET_REGION_INFO:
+		return nvgrace_gpu_ioctl_get_region_info(core_vdev,
arg);
+	case VFIO_DEVICE_IOEVENTFD:
+		return -ENOTTY;
+	case VFIO_DEVICE_RESET:
+		nvgrace_gpu_init_fake_bar_emu_regs(core_vdev);
+		fallthrough;
+	default:
+		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
+	}
+}
+
+static __le64
+nvgrace_gpu_get_read_value(size_t bar_size, u64 flags, __le64 val64)
+{
+	u64 tmp_val;
+
+	tmp_val = le64_to_cpu(val64);
+	tmp_val &= ~(bar_size - 1);
+	tmp_val |= flags;
+
+	return cpu_to_le64(tmp_val);
+}
+
+/*
+ * Both the usable (usemem) and the reserved (resmem) device memory
region
+ * are exposed as a 64b fake device BARs in the VM. These fake BARs
must
+ * respond to the accesses on their respective PCI config space
offsets.
+ *
+ * resmem BAR owns PCI_BASE_ADDRESS_2 & PCI_BASE_ADDRESS_3.
+ * usemem BAR owns PCI_BASE_ADDRESS_4 & PCI_BASE_ADDRESS_5.
+ */
+static ssize_t
+nvgrace_gpu_read_config_emu(struct vfio_device *core_vdev,
+			    char __user *buf, size_t count, loff_t
*ppos) +{
+	struct nvgrace_gpu_pci_core_device *nvdev =
+		container_of(core_vdev, struct
nvgrace_gpu_pci_core_device,
+			     core_device.vdev);
+	u64 pos = *ppos & VFIO_PCI_OFFSET_MASK;
+	struct mem_region *memregion = NULL;
+	__le64 val64;
+	size_t register_offset;
+	loff_t copy_offset;
+	size_t copy_count;
+	int ret;
+
+	ret = vfio_pci_core_read(core_vdev, buf, count, ppos);
+	if (ret < 0)
+		return ret;
+
+	if (vfio_pci_core_range_intersect_range(pos, count,
PCI_BASE_ADDRESS_2,
+						sizeof(val64),
+						&copy_offset,
&copy_count,
+						&register_offset))
+		memregion =
nvgrace_gpu_memregion(RESMEM_REGION_INDEX, nvdev);
+	else if (vfio_pci_core_range_intersect_range(pos, count,
+
PCI_BASE_ADDRESS_4,
+						     sizeof(val64),
+						     &copy_offset,
&copy_count,
+
&register_offset))
+		memregion =
nvgrace_gpu_memregion(USEMEM_REGION_INDEX, nvdev); +
+	if (memregion) {
+		val64 =
nvgrace_gpu_get_read_value(memregion->bar_size,
+
PCI_BASE_ADDRESS_MEM_TYPE_64 |
+
PCI_BASE_ADDRESS_MEM_PREFETCH,
+
memregion->bar_val);
+		if (copy_to_user(buf + copy_offset,
+				 (void *)&val64 + register_offset,
copy_count)) {
+			/*
+			 * The position has been incremented in
+			 * vfio_pci_core_read. Reset the offset back
to the
+			 * starting position.
+			 */
+			*ppos -= count;
+			return -EFAULT;
+		}
+	}
+
+	return count;
+}
+
+static ssize_t
+nvgrace_gpu_write_config_emu(struct vfio_device *core_vdev,
+			     const char __user *buf, size_t count,
loff_t *ppos) +{
+	struct nvgrace_gpu_pci_core_device *nvdev =
+		container_of(core_vdev, struct
nvgrace_gpu_pci_core_device,
+			     core_device.vdev);
+	u64 pos = *ppos & VFIO_PCI_OFFSET_MASK;
+	struct mem_region *memregion = NULL;
+	size_t register_offset;
+	loff_t copy_offset;
+	size_t copy_count;
+
+	if (vfio_pci_core_range_intersect_range(pos, count,
PCI_BASE_ADDRESS_2,
+						sizeof(u64),
&copy_offset,
+						&copy_count,
&register_offset))
+		memregion =
nvgrace_gpu_memregion(RESMEM_REGION_INDEX, nvdev);
+	else if (vfio_pci_core_range_intersect_range(pos, count,
PCI_BASE_ADDRESS_4,
+						     sizeof(u64),
&copy_offset,
+						     &copy_count,
&register_offset))
+		memregion =
nvgrace_gpu_memregion(USEMEM_REGION_INDEX, nvdev); +
+	if (memregion) {
+		if (copy_from_user((void *)&memregion->bar_val +
register_offset,
+				   buf + copy_offset, copy_count))
+			return -EFAULT;
+		*ppos += copy_count;
+		return copy_count;
+	}
+
+	return vfio_pci_core_write(core_vdev, buf, count, ppos);
+}
+
+/*
+ * Ad hoc map the device memory in the module kernel VA space.
Primarily needed
+ * as vfio does not require the userspace driver to only perform
accesses through
+ * mmaps of the vfio-pci BAR regions and such accesses should be
supported using
+ * vfio_device_ops read/write implementations.
+ *
+ * The usemem region is cacheable memory and hence is memremaped.
+ * The resmem region is non-cached and is mapped using ioremap_wc
(NORMAL_NC).
+ */
+static int
+nvgrace_gpu_map_device_mem(int index,
+			   struct nvgrace_gpu_pci_core_device *nvdev)
+{
+	struct mem_region *memregion;
+	int ret = 0;
+
+	memregion = nvgrace_gpu_memregion(index, nvdev);
+	if (!memregion)
+		return -EINVAL;
+
+	mutex_lock(&nvdev->remap_lock);
+
+	if (memregion->memaddr)
+		goto unlock;
+
+	if (index == USEMEM_REGION_INDEX)
+		memregion->memaddr = memremap(memregion->memphys,
+					      memregion->memlength,
+					      MEMREMAP_WB);
+	else
+		memregion->ioaddr = ioremap_wc(memregion->memphys,
+					       memregion->memlength);
+
+	if (!memregion->memaddr)
+		ret = -ENOMEM;
+
+unlock:
+	mutex_unlock(&nvdev->remap_lock);
+
+	return ret;
+}
+
+/*
+ * Read the data from the device memory (mapped either through
ioremap
+ * or memremap) into the user buffer.
+ */
+static int
+nvgrace_gpu_map_and_read(struct nvgrace_gpu_pci_core_device *nvdev,
+			 char __user *buf, size_t mem_count, loff_t
*ppos) +{
+	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	u64 offset = *ppos & VFIO_PCI_OFFSET_MASK;
+	int ret;
+
+	if (!mem_count)
+		return 0;
+
+	/*
+	 * Handle read on the BAR regions. Map to the target device
memory
+	 * physical address and copy to the request read buffer.
+	 */
+	ret = nvgrace_gpu_map_device_mem(index, nvdev);
+	if (ret)
+		return ret;
+
+	if (index == USEMEM_REGION_INDEX) {
+		if (copy_to_user(buf,
+				 (u8 *)nvdev->usemem.memaddr +
offset,
+				 mem_count))
+			ret = -EFAULT;
+	} else {
+		/*
+		 * The hardware ensures that the system does not
crash when
+		 * the device memory is accessed with the memory
enable
+		 * turned off. It synthesizes ~0 on such read. So
there is
+		 * no need to check or support the
disablement/enablement of
+		 * BAR through PCI_COMMAND config space register.
Pass
+		 * test_mem flag as false.
+		 */
+		ret = vfio_pci_core_do_io_rw(&nvdev->core_device,
false,
+					     nvdev->resmem.ioaddr,
+					     buf, offset, mem_count,
+					     0, 0, false);
+	}
+
+	return ret;
+}
+
+/*
+ * Read count bytes from the device memory at an offset. The actual
device
+ * memory size (available) may not be a power-of-2. So the driver
fakes
+ * the size to a power-of-2 (reported) when exposing to a user space
driver.
+ *
+ * Reads starting beyond the reported size generate -EINVAL; reads
extending
+ * beyond the actual device size is filled with ~0; reads extending
beyond
+ * the reported size are truncated.
+ */
+static ssize_t
+nvgrace_gpu_read_mem(struct nvgrace_gpu_pci_core_device *nvdev,
+		     char __user *buf, size_t count, loff_t *ppos)
+{
+	u64 offset = *ppos & VFIO_PCI_OFFSET_MASK;
+	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	struct mem_region *memregion;
+	size_t mem_count, i;
+	u8 val = 0xFF;
+	int ret;
+
+	memregion = nvgrace_gpu_memregion(index, nvdev);
+	if (!memregion)
+		return -EINVAL;
+
+	if (offset >= memregion->bar_size)
+		return -EINVAL;
+
+	/* Clip short the read request beyond reported BAR size */
+	count = min(count, memregion->bar_size - (size_t)offset);
+
+	/*
+	 * Determine how many bytes to be actually read from the
device memory.
+	 * Read request beyond the actual device memory size is
filled with ~0,
+	 * while those beyond the actual reported size is skipped.
+	 */
+	if (offset >= memregion->memlength)
+		mem_count = 0;
+	else
+		mem_count = min(count, memregion->memlength -
(size_t)offset); +
+	ret = nvgrace_gpu_map_and_read(nvdev, buf, mem_count, ppos);
+	if (ret)
+		return ret;
+
+	/*
+	 * Only the device memory present on the hardware is mapped,
which may
+	 * not be power-of-2 aligned. A read to an offset beyond the
device memory
+	 * size is filled with ~0.
+	 */
+	for (i = mem_count; i < count; i++)
+		put_user(val, (unsigned char __user *)(buf + i));
+
+	*ppos += count;
+	return count;
+}
+
+static ssize_t
+nvgrace_gpu_read(struct vfio_device *core_vdev,
+		 char __user *buf, size_t count, loff_t *ppos)
+{
+	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	struct nvgrace_gpu_pci_core_device *nvdev =
+		container_of(core_vdev, struct
nvgrace_gpu_pci_core_device,
+			     core_device.vdev);
+
+	if (nvgrace_gpu_memregion(index, nvdev))
+		return nvgrace_gpu_read_mem(nvdev, buf, count, ppos);
+
+	if (index == VFIO_PCI_CONFIG_REGION_INDEX)
+		return nvgrace_gpu_read_config_emu(core_vdev, buf,
count, ppos); +
+	return vfio_pci_core_read(core_vdev, buf, count, ppos);
+}
+
+/*
+ * Write the data to the device memory (mapped either through ioremap
+ * or memremap) from the user buffer.
+ */
+static int
+nvgrace_gpu_map_and_write(struct nvgrace_gpu_pci_core_device *nvdev,
+			  const char __user *buf, size_t mem_count,
+			  loff_t *ppos)
+{
+	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+	int ret;
+
+	if (!mem_count)
+		return 0;
+
+	ret = nvgrace_gpu_map_device_mem(index, nvdev);
+	if (ret)
+		return ret;
+
+	if (index == USEMEM_REGION_INDEX) {
+		if (copy_from_user((u8 *)nvdev->usemem.memaddr + pos,
+				   buf, mem_count))
+			return -EFAULT;
+	} else {
+		/*
+		 * The hardware ensures that the system does not
crash when
+		 * the device memory is accessed with the memory
enable
+		 * turned off. It drops such writes. So there is no
need to
+		 * check or support the disablement/enablement of BAR
+		 * through PCI_COMMAND config space register. Pass
test_mem
+		 * flag as false.
+		 */
+		ret = vfio_pci_core_do_io_rw(&nvdev->core_device,
false,
+					     nvdev->resmem.ioaddr,
+					     (char __user *)buf,
pos, mem_count,
+					     0, 0, true);
+	}
+
+	return ret;
+}
+
+/*
+ * Write count bytes to the device memory at a given offset. The
actual device
+ * memory size (available) may not be a power-of-2. So the driver
fakes the
+ * size to a power-of-2 (reported) when exposing to a user space
driver.
+ *
+ * Writes extending beyond the reported size are truncated; writes
starting
+ * beyond the reported size generate -EINVAL.
+ */
+static ssize_t
+nvgrace_gpu_write_mem(struct nvgrace_gpu_pci_core_device *nvdev,
+		      size_t count, loff_t *ppos, const char __user
*buf) +{
+	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	u64 offset = *ppos & VFIO_PCI_OFFSET_MASK;
+	struct mem_region *memregion;
+	size_t mem_count;
+	int ret = 0;
+
+	memregion = nvgrace_gpu_memregion(index, nvdev);
+	if (!memregion)
+		return -EINVAL;
+
+	if (offset >= memregion->bar_size)
+		return -EINVAL;
+
+	/* Clip short the write request beyond reported BAR size */
+	count = min(count, memregion->bar_size - (size_t)offset);
+
+	/*
+	 * Determine how many bytes to be actually written to the
device memory.
+	 * Do not write to the offset beyond available size.
+	 */
+	if (offset >= memregion->memlength)
+		goto exitfn;
+
+	/*
+	 * Only the device memory present on the hardware is mapped,
which may
+	 * not be power-of-2 aligned. Drop access outside the
available device
+	 * memory on the hardware.
+	 */
+	mem_count = min(count, memregion->memlength -
(size_t)offset); +
+	ret = nvgrace_gpu_map_and_write(nvdev, buf, mem_count, ppos);
+	if (ret)
+		return ret;
+
+exitfn:
+	*ppos += count;
+	return count;
+}
+
+static ssize_t
+nvgrace_gpu_write(struct vfio_device *core_vdev,
+		  const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct nvgrace_gpu_pci_core_device *nvdev =
+		container_of(core_vdev, struct
nvgrace_gpu_pci_core_device,
+			     core_device.vdev);
+	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+
+	if (nvgrace_gpu_memregion(index, nvdev))
+		return nvgrace_gpu_write_mem(nvdev, count, ppos,
buf); +
+	if (index == VFIO_PCI_CONFIG_REGION_INDEX)
+		return nvgrace_gpu_write_config_emu(core_vdev, buf,
count, ppos); +
+	return vfio_pci_core_write(core_vdev, buf, count, ppos);
+}
+
+static const struct vfio_device_ops nvgrace_gpu_pci_ops = {
+	.name		= "nvgrace-gpu-vfio-pci",
+	.init		= vfio_pci_core_init_dev,
+	.release	= vfio_pci_core_release_dev,
+	.open_device	= nvgrace_gpu_open_device,
+	.close_device	= nvgrace_gpu_close_device,
+	.ioctl		= nvgrace_gpu_ioctl,
+	.read		= nvgrace_gpu_read,
+	.write		= nvgrace_gpu_write,
+	.mmap		= nvgrace_gpu_mmap,
+	.request	= vfio_pci_core_request,
+	.match		= vfio_pci_core_match,
+	.bind_iommufd	= vfio_iommufd_physical_bind,
+	.unbind_iommufd	= vfio_iommufd_physical_unbind,
+	.attach_ioas	= vfio_iommufd_physical_attach_ioas,
+	.detach_ioas	= vfio_iommufd_physical_detach_ioas,
+};
+
+static const struct vfio_device_ops nvgrace_gpu_pci_core_ops = {
+	.name		= "nvgrace-gpu-vfio-pci-core",
+	.init		= vfio_pci_core_init_dev,
+	.release	= vfio_pci_core_release_dev,
+	.open_device	= nvgrace_gpu_open_device,
+	.close_device	= vfio_pci_core_close_device,
+	.ioctl		= vfio_pci_core_ioctl,
+	.device_feature	= vfio_pci_core_ioctl_feature,
+	.read		= vfio_pci_core_read,
+	.write		= vfio_pci_core_write,
+	.mmap		= vfio_pci_core_mmap,
+	.request	= vfio_pci_core_request,
+	.match		= vfio_pci_core_match,
+	.bind_iommufd	= vfio_iommufd_physical_bind,
+	.unbind_iommufd	= vfio_iommufd_physical_unbind,
+	.attach_ioas	= vfio_iommufd_physical_attach_ioas,
+	.detach_ioas	= vfio_iommufd_physical_detach_ioas,
+};
+
+static struct
+nvgrace_gpu_pci_core_device *nvgrace_gpu_drvdata(struct pci_dev
*pdev) +{
+	struct vfio_pci_core_device *core_device =
dev_get_drvdata(&pdev->dev); +
+	return container_of(core_device, struct
nvgrace_gpu_pci_core_device,
+			    core_device);
+}
+
+static int
+nvgrace_gpu_fetch_memory_property(struct pci_dev *pdev,
+				  u64 *pmemphys, u64 *pmemlength)
+{
+	int ret;
+
+	/*
+	 * The memory information is present in the system ACPI
tables as DSD
+	 * properties nvidia,gpu-mem-base-pa and nvidia,gpu-mem-size.
+	 */
+	ret = device_property_read_u64(&pdev->dev,
"nvidia,gpu-mem-base-pa",
+				       pmemphys);
+	if (ret)
+		return ret;
+
+	if (*pmemphys > type_max(phys_addr_t))
+		return -EOVERFLOW;
+
+	ret = device_property_read_u64(&pdev->dev,
"nvidia,gpu-mem-size",
+				       pmemlength);
+	if (ret)
+		return ret;
+
+	if (*pmemlength > type_max(size_t))
+		return -EOVERFLOW;
+
+	/*
+	 * If the C2C link is not up due to an error, the coherent
device
+	 * memory size is returned as 0. Fail in such case.
+	 */
+	if (*pmemlength == 0)
+		return -ENOMEM;
+
+	return ret;
+}
+
+static int
+nvgrace_gpu_init_nvdev_struct(struct pci_dev *pdev,
+			      struct nvgrace_gpu_pci_core_device
*nvdev,
+			      u64 memphys, u64 memlength)
+{
+	int ret = 0;
+
+	/*
+	 * The VM GPU device driver needs a non-cacheable region to
support
+	 * the MIG feature. Since the device memory is mapped as
NORMAL cached,
+	 * carve out a region from the end with a different NORMAL_NC
+	 * property (called as reserved memory and represented as
resmem). This
+	 * region then is exposed as a 64b BAR (region 2 and 3) to
the VM, while
+	 * exposing the rest (termed as usable memory and
represented using usemem)
+	 * as cacheable 64b BAR (region 4 and 5).
+	 *
+	 *               devmem (memlength)
+	 * |-------------------------------------------------|
+	 * |                                           |
+	 * usemem.memphys                              resmem.memphys
+	 */
+	nvdev->usemem.memphys = memphys;
+
+	/*
+	 * The device memory exposed to the VM is added to the
kernel by the
+	 * VM driver module in chunks of memory block size. Only the
usable
+	 * memory (usemem) is added to the kernel for usage by the VM
+	 * workloads. Make the usable memory size memblock aligned.
+	 */
+	if (check_sub_overflow(memlength, RESMEM_SIZE,
+			       &nvdev->usemem.memlength)) {
+		ret = -EOVERFLOW;
+		goto done;
+	}
+
+	/*
+	 * The USEMEM part of the device memory has to be MEMBLK_SIZE
+	 * aligned. This is a hardwired ABI value between the GPU FW
and
+	 * VFIO driver. The VM device driver is also aware of it and
make
+	 * use of the value for its calculation to determine USEMEM
size.
+	 */
+	nvdev->usemem.memlength = round_down(nvdev->usemem.memlength,
+					     MEMBLK_SIZE);
+	if ((check_add_overflow(nvdev->usemem.memphys,
+				nvdev->usemem.memlength,
+				&nvdev->resmem.memphys)) ||
+	    (check_sub_overflow(memlength, nvdev->usemem.memlength,
+				&nvdev->resmem.memlength))) {
+		ret = -EOVERFLOW;
+		goto done;
+	}
+
+	if (nvdev->usemem.memlength == 0) {
+		ret = -EINVAL;
+		goto done;
+	}
+
+	/*
+	 * The memory regions are exposed as BARs. Calculate and save
+	 * the BAR size for them.
+	 */
+	nvdev->usemem.bar_size =
roundup_pow_of_two(nvdev->usemem.memlength);
+	nvdev->resmem.bar_size =
roundup_pow_of_two(nvdev->resmem.memlength); +done:
+	return ret;
+}
+
+static int nvgrace_gpu_probe(struct pci_dev *pdev,
+			     const struct pci_device_id *id)
+{
+	const struct vfio_device_ops *ops =
&nvgrace_gpu_pci_core_ops;
+	struct nvgrace_gpu_pci_core_device *nvdev;
+	u64 memphys, memlength;
+	int ret;
+
+	ret = nvgrace_gpu_fetch_memory_property(pdev, &memphys,
&memlength);
+	if (!ret)
+		ops = &nvgrace_gpu_pci_ops;
+
+	nvdev = vfio_alloc_device(nvgrace_gpu_pci_core_device,
core_device.vdev,
+				  &pdev->dev, ops);
+	if (IS_ERR(nvdev))
+		return PTR_ERR(nvdev);
+
+	dev_set_drvdata(&pdev->dev, &nvdev->core_device);
+
+	if (ops == &nvgrace_gpu_pci_ops) {
+		/*
+		 * Device memory properties are identified in the
host ACPI
+		 * table. Set the nvgrace_gpu_pci_core_device
structure.
+		 */
+		ret = nvgrace_gpu_init_nvdev_struct(pdev, nvdev,
+						    memphys,
memlength);
+		if (ret)
+			goto out_put_vdev;
+	}
+
+	ret = vfio_pci_core_register_device(&nvdev->core_device);
+	if (ret)
+		goto out_put_vdev;
+
+	return ret;
+
+out_put_vdev:
+	vfio_put_device(&nvdev->core_device.vdev);
+	return ret;
+}
+
+static void nvgrace_gpu_remove(struct pci_dev *pdev)
+{
+	struct nvgrace_gpu_pci_core_device *nvdev =
nvgrace_gpu_drvdata(pdev);
+	struct vfio_pci_core_device *vdev = &nvdev->core_device;
+
+	vfio_pci_core_unregister_device(vdev);
+	vfio_put_device(&vdev->vdev);
+}
+
+static const struct pci_device_id nvgrace_gpu_vfio_pci_table[] = {
+	/* GH200 120GB */
+	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_NVIDIA,
0x2342) },
+	/* GH200 480GB */
+	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_NVIDIA,
0x2345) },
+	{}
+};
+
+MODULE_DEVICE_TABLE(pci, nvgrace_gpu_vfio_pci_table);
+
+static struct pci_driver nvgrace_gpu_vfio_pci_driver = {
+	.name = KBUILD_MODNAME,
+	.id_table = nvgrace_gpu_vfio_pci_table,
+	.probe = nvgrace_gpu_probe,
+	.remove = nvgrace_gpu_remove,
+	.err_handler = &vfio_pci_core_err_handlers,
+	.driver_managed_dma = true,
+};
+
+module_pci_driver(nvgrace_gpu_vfio_pci_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Ankit Agrawal [off-list ref]");
+MODULE_AUTHOR("Aniket Agashe [off-list ref]");
+MODULE_DESCRIPTION("VFIO NVGRACE GPU PF - User Level driver for
NVIDIA devices with CPU coherently accessible device memory");