diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index 1e82b44bda1a..296bf01e185e 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -60,6 +60,8 @@ config VFIO_PCI_DMABUF
 
 source "drivers/vfio/pci/mlx5/Kconfig"
 
+source "drivers/vfio/pci/ism/Kconfig"
+
 source "drivers/vfio/pci/hisilicon/Kconfig"
 
 source "drivers/vfio/pci/pds/Kconfig"
diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
index e0a0757dd1d2..6138f1bf241d 100644
--- a/drivers/vfio/pci/Makefile
+++ b/drivers/vfio/pci/Makefile
@@ -11,6 +11,8 @@ obj-$(CONFIG_VFIO_PCI) += vfio-pci.o
 
 obj-$(CONFIG_MLX5_VFIO_PCI)           += mlx5/
 
+obj-$(CONFIG_ISM_VFIO_PCI)           += ism/
+
 obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/
 
 obj-$(CONFIG_PDS_VFIO_PCI) += pds/
diff --git a/drivers/vfio/pci/ism/Kconfig b/drivers/vfio/pci/ism/Kconfig
new file mode 100644
index 000000000000..02f47d25fed2
--- /dev/null
+++ b/drivers/vfio/pci/ism/Kconfig
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0
+config ISM_VFIO_PCI
+	tristate "VFIO support for ISM devices"
+	depends on S390
+	select VFIO_PCI_CORE
+	help
+	  This provides user space support for IBM Internal Shared Memory (ISM)
+	  Adapter devices using the VFIO framework.
+
+	  If you don't know what to do here, say N.
diff --git a/drivers/vfio/pci/ism/Makefile b/drivers/vfio/pci/ism/Makefile
new file mode 100644
index 000000000000..32cc3c66dd11
--- /dev/null
+++ b/drivers/vfio/pci/ism/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_ISM_VFIO_PCI) += ism-vfio-pci.o
+ism-vfio-pci-y := main.o
diff --git a/drivers/vfio/pci/ism/main.c b/drivers/vfio/pci/ism/main.c
new file mode 100644
index 000000000000..f83e09b915ed
--- /dev/null
+++ b/drivers/vfio/pci/ism/main.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * vfio-ISM driver for s390
+ *
+ * Copyright IBM Corp.
+ */
+
+#include <linux/slab.h>
+#include "../vfio_pci_priv.h"
+
+#define ISM_VFIO_PCI_OFFSET_SHIFT   48
+#define ISM_VFIO_PCI_OFFSET_TO_INDEX(off) ((off) >> ISM_VFIO_PCI_OFFSET_SHIFT)
+#define ISM_VFIO_PCI_INDEX_TO_OFFSET(index) ((u64)(index) << ISM_VFIO_PCI_OFFSET_SHIFT)
+#define ISM_VFIO_PCI_OFFSET_MASK (((u64)(1) << ISM_VFIO_PCI_OFFSET_SHIFT) - 1)
+
+/*
+ * Use __zpci_load() to bypass automatic use of
+ * PCI MIO instructions which are not supported on ISM devices
+ */
+#define ISM_READ(size)                                                        \
+	static int ism_read##size(struct zpci_dev *zdev, int bar,             \
+				  size_t *filled, char __user *buf,           \
+				  loff_t off)                                 \
+	{                                                                     \
+		u64 req, tmp;                                                 \
+		u##size val;                                                  \
+		int ret;                                                      \
+									      \
+		req = ZPCI_CREATE_REQ(READ_ONCE(zdev->fh), bar, sizeof(val)); \
+		ret = __zpci_load(&tmp, req, off);                            \
+		if (ret)                                                      \
+			return ret;                                           \
+		val = (u##size)tmp;                                           \
+		if (copy_to_user(buf, &val, sizeof(val)))                     \
+			return -EFAULT;                                       \
+		*filled = sizeof(val);                                        \
+		return 0;						      \
+	}
+
+ISM_READ(64);
+ISM_READ(32);
+ISM_READ(16);
+ISM_READ(8);
+
+struct ism_vfio_pci_core_device {
+	struct vfio_pci_core_device core_device;
+	struct kmem_cache *store_block_cache;
+};
+
+static int ism_vfio_pci_open_device(struct vfio_device *core_vdev)
+{
+	struct ism_vfio_pci_core_device *ivpcd;
+	struct vfio_pci_core_device *vdev;
+	int ret;
+
+	ivpcd = container_of(core_vdev, struct ism_vfio_pci_core_device,
+			     core_device.vdev);
+	vdev = &ivpcd->core_device;
+
+	ret = vfio_pci_core_enable(vdev);
+	if (ret)
+		return ret;
+
+	vfio_pci_core_finish_enable(vdev);
+	return 0;
+}
+
+/*
+ * ism_vfio_pci_do_io_r()
+ *
+ * On s390, kernel primitives such as ioread() and iowrite() are switched over
+ * from function-handle-based PCI load/stores instructions to PCI memory-I/O (MIO)
+ * loads/stores when these are available and not explicitly disabled. Since these
+ * instructions cannot be used with ISM devices, ensure that classic
+ * function-handle-based PCI instructions are used instead.
+ */
+static ssize_t ism_vfio_pci_do_io_r(struct vfio_pci_core_device *vdev,
+				    char __user *buf, loff_t off, size_t count,
+				    int bar)
+{
+	struct zpci_dev *zdev = to_zpci(vdev->pdev);
+	ssize_t done = 0;
+	int ret;
+
+	while (count) {
+		size_t filled;
+
+		if (count >= 8 && IS_ALIGNED(off, 8)) {
+			ret = ism_read64(zdev, bar, &filled, buf, off);
+			if (ret)
+				return ret;
+		} else if (count >= 4 && IS_ALIGNED(off, 4)) {
+			ret = ism_read32(zdev, bar, &filled, buf, off);
+			if (ret)
+				return ret;
+		} else if (count >= 2 && IS_ALIGNED(off, 2)) {
+			ret = ism_read16(zdev, bar, &filled, buf, off);
+			if (ret)
+				return ret;
+		} else {
+			ret = ism_read8(zdev, bar, &filled, buf, off);
+			if (ret)
+				return ret;
+		}
+
+		count -= filled;
+		done += filled;
+		off += filled;
+		buf += filled;
+	}
+
+	return done;
+}
+
+/*
+ * ism_vfio_pci_do_io_w()
+ *
+ * Ensure that the PCI store block (PCISTB) instruction is used as required by the
+ * ISM device. The ISM device also uses a 256 TiB BAR 0 for write operations,
+ * which requires a 48bit region address space (ISM_VFIO_PCI_OFFSET_SHIFT).
+ */
+static ssize_t ism_vfio_pci_do_io_w(struct vfio_pci_core_device *vdev,
+				    char __user *buf, loff_t off, size_t count,
+				    int bar)
+{
+	struct zpci_dev *zdev = to_zpci(vdev->pdev);
+	struct ism_vfio_pci_core_device *ivpcd;
+	ssize_t ret;
+	void *data;
+	u64 req;
+
+	if (count > zdev->maxstbl)
+		return -EINVAL;
+	if (((off % PAGE_SIZE) + count) > PAGE_SIZE)
+		return -EINVAL;
+
+	ivpcd = container_of(vdev, struct ism_vfio_pci_core_device,
+			     core_device);
+	data = kmem_cache_alloc(ivpcd->store_block_cache, GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	if (copy_from_user(data, buf, count)) {
+		ret = -EFAULT;
+		goto out_free;
+	}
+
+	req = ZPCI_CREATE_REQ(READ_ONCE(zdev->fh), bar, count);
+	ret = __zpci_store_block(data, req, off);
+	if (ret)
+		goto out_free;
+
+	ret = count;
+
+out_free:
+	kmem_cache_free(ivpcd->store_block_cache, data);
+	return ret;
+}
+
+static ssize_t ism_vfio_pci_bar_rw(struct vfio_pci_core_device *vdev,
+				   char __user *buf, size_t count, loff_t *ppos,
+				   bool iswrite)
+{
+	int bar = ISM_VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	loff_t pos = *ppos & ISM_VFIO_PCI_OFFSET_MASK;
+	resource_size_t end;
+	ssize_t done = 0;
+
+	if (pci_resource_start(vdev->pdev, bar))
+		end = pci_resource_len(vdev->pdev, bar);
+	else
+		return -EINVAL;
+
+	if (pos >= end)
+		return -EINVAL;
+
+	count = min(count, (size_t)(end - pos));
+
+	if (iswrite)
+		done = ism_vfio_pci_do_io_w(vdev, buf, pos, count, bar);
+	else
+		done = ism_vfio_pci_do_io_r(vdev, buf, pos, count, bar);
+
+	if (done >= 0)
+		*ppos += done;
+
+	return done;
+}
+
+static ssize_t ism_vfio_pci_config_rw(struct vfio_pci_core_device *vdev,
+				      char __user *buf, size_t count,
+				      loff_t *ppos, bool iswrite)
+{
+	loff_t pos = *ppos;
+	size_t done = 0;
+	int ret = 0;
+
+	pos &= ISM_VFIO_PCI_OFFSET_MASK;
+
+	while (count) {
+		/*
+		 * zPCI must not use MIO instructions for config space access,
+		 * so we can use common code path here.
+		 */
+		ret = vfio_pci_config_rw_single(vdev, buf, count, &pos, iswrite);
+		if (ret < 0)
+			return ret;
+
+		count -= ret;
+		done += ret;
+		buf += ret;
+		pos += ret;
+	}
+
+	*ppos += done;
+
+	return done;
+}
+
+static ssize_t ism_vfio_pci_rw(struct vfio_device *core_vdev, char __user *buf,
+			       size_t count, loff_t *ppos, bool iswrite)
+{
+	unsigned int index = ISM_VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	struct vfio_pci_core_device *vdev;
+	int ret;
+
+	vdev = container_of(core_vdev, struct vfio_pci_core_device, vdev);
+
+	if (!count)
+		return 0;
+
+	switch (index) {
+	case VFIO_PCI_CONFIG_REGION_INDEX:
+		ret = ism_vfio_pci_config_rw(vdev, buf, count, ppos, iswrite);
+		break;
+
+	case VFIO_PCI_BAR0_REGION_INDEX ... VFIO_PCI_BAR5_REGION_INDEX:
+		ret = ism_vfio_pci_bar_rw(vdev, buf, count, ppos, iswrite);
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static ssize_t ism_vfio_pci_read(struct vfio_device *core_vdev,
+				 char __user *buf, size_t count, loff_t *ppos)
+{
+	return ism_vfio_pci_rw(core_vdev, buf, count, ppos, false);
+}
+
+static ssize_t ism_vfio_pci_write(struct vfio_device *core_vdev,
+				  const char __user *buf, size_t count,
+				  loff_t *ppos)
+{
+	return ism_vfio_pci_rw(core_vdev, (char __user *)buf, count, ppos,
+			       true);
+}
+
+static int ism_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
+					      struct vfio_region_info *info,
+					      struct vfio_info_cap *caps)
+{
+	struct vfio_pci_core_device *vdev =
+		container_of(core_vdev, struct vfio_pci_core_device, vdev);
+	struct pci_dev *pdev = vdev->pdev;
+
+	switch (info->index) {
+	case VFIO_PCI_CONFIG_REGION_INDEX:
+		info->offset = ISM_VFIO_PCI_INDEX_TO_OFFSET(info->index);
+		info->size = pdev->cfg_size;
+		info->flags = VFIO_REGION_INFO_FLAG_READ |
+			      VFIO_REGION_INFO_FLAG_WRITE;
+		break;
+	case VFIO_PCI_BAR0_REGION_INDEX ... VFIO_PCI_BAR5_REGION_INDEX:
+		info->offset = ISM_VFIO_PCI_INDEX_TO_OFFSET(info->index);
+		info->size = pci_resource_len(pdev, info->index);
+		if (!info->size) {
+			info->flags = 0;
+			break;
+		}
+		info->flags = VFIO_REGION_INFO_FLAG_READ |
+			      VFIO_REGION_INFO_FLAG_WRITE;
+		break;
+	default:
+		info->offset = 0;
+		info->size = 0;
+		info->flags = 0;
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int ism_vfio_pci_init_dev(struct vfio_device *core_vdev)
+{
+	struct zpci_dev *zdev = to_zpci(to_pci_dev(core_vdev->dev));
+	struct ism_vfio_pci_core_device *ivpcd;
+	char cache_name[20];
+	int ret;
+
+	ivpcd = container_of(core_vdev, struct ism_vfio_pci_core_device,
+			     core_device.vdev);
+
+	snprintf(cache_name, sizeof(cache_name), "ism_sb_fid_%08x", zdev->fid);
+
+	ivpcd->store_block_cache =
+		kmem_cache_create(cache_name, zdev->maxstbl,
+				  (&(struct kmem_cache_args){
+					  .align = PAGE_SIZE,
+					  .useroffset = 0,
+					  .usersize = zdev->maxstbl,
+				  }),
+				  (SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT));
+	if (!ivpcd->store_block_cache)
+		return -ENOMEM;
+
+	ret = vfio_pci_core_init_dev(core_vdev);
+	if (ret)
+		kmem_cache_destroy(ivpcd->store_block_cache);
+
+	return ret;
+}
+
+static void ism_vfio_pci_release_dev(struct vfio_device *core_vdev)
+{
+	struct ism_vfio_pci_core_device *ivpcd = container_of(
+		core_vdev, struct ism_vfio_pci_core_device, core_device.vdev);
+
+	kmem_cache_destroy(ivpcd->store_block_cache);
+	vfio_pci_core_release_dev(core_vdev);
+}
+
+static const struct vfio_device_ops ism_pci_ops = {
+	.name = "ism-vfio-pci",
+	.init = ism_vfio_pci_init_dev,
+	.release = ism_vfio_pci_release_dev,
+	.open_device = ism_vfio_pci_open_device,
+	.close_device = vfio_pci_core_close_device,
+	.ioctl = vfio_pci_core_ioctl,
+	.get_region_info_caps = ism_vfio_pci_ioctl_get_region_info,
+	.device_feature = vfio_pci_core_ioctl_feature,
+	.read = ism_vfio_pci_read,
+	.write = ism_vfio_pci_write,
+	.request = vfio_pci_core_request,
+	.match = vfio_pci_core_match,
+	.match_token_uuid = vfio_pci_core_match_token_uuid,
+	.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 int ism_vfio_pci_probe(struct pci_dev *pdev,
+			      const struct pci_device_id *id)
+{
+	struct ism_vfio_pci_core_device *ivpcd;
+	int ret;
+
+	ivpcd = vfio_alloc_device(ism_vfio_pci_core_device, core_device.vdev,
+				  &pdev->dev, &ism_pci_ops);
+	if (IS_ERR(ivpcd))
+		return PTR_ERR(ivpcd);
+
+	dev_set_drvdata(&pdev->dev, &ivpcd->core_device);
+
+	ret = vfio_pci_core_register_device(&ivpcd->core_device);
+	if (ret)
+		vfio_put_device(&ivpcd->core_device.vdev);
+
+	return ret;
+}
+
+static void ism_vfio_pci_remove(struct pci_dev *pdev)
+{
+	struct vfio_pci_core_device *core_device;
+	struct ism_vfio_pci_core_device *ivpcd;
+
+	core_device = dev_get_drvdata(&pdev->dev);
+	ivpcd = container_of(core_device, struct ism_vfio_pci_core_device,
+			     core_device);
+
+	vfio_pci_core_unregister_device(&ivpcd->core_device);
+	vfio_put_device(&ivpcd->core_device.vdev);
+}
+
+static const struct pci_device_id ism_device_table[] = {
+	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_IBM,
+					  PCI_DEVICE_ID_IBM_ISM) },
+	{}
+};
+MODULE_DEVICE_TABLE(pci, ism_device_table);
+
+static struct pci_driver ism_vfio_pci_driver = {
+	.name = KBUILD_MODNAME,
+	.id_table = ism_device_table,
+	.probe = ism_vfio_pci_probe,
+	.remove = ism_vfio_pci_remove,
+	.err_handler = &vfio_pci_core_err_handlers,
+	.driver_managed_dma = true,
+};
+
+module_pci_driver(ism_vfio_pci_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("vfio-pci variant driver for the IBM Internal Shared Memory (ISM) device");
+MODULE_AUTHOR("IBM Corporation");