[RFC v1 1/2] uio: Add SVA support for PCI devices via uio_pci_generic_sva.c

[RFC v1 1/2] uio: Add SVA support for PCI devices via uio_pci_generic_sva.c

[Yaxing Guo]

This patch introduces a new UIO driver, uio_pci_generic_sva, which
extends the functionality of uio_pci_generic by adding support for
Shared Virtual Addressing (SVA) when IOMMU is enabled in the system.

The key enhancement allows PCI devices to directly use user-space virtual
addresses for DMA operations, eliminating the need for bounce buffers or
explicit IOVA mapping. This is achieved by leveraging the kernel's IOMMU-SVA
subsystem, including process address space attachment, page fault handling,
and shared context management between CPU and device.

With this driver, userspace applications can perform zero-copy DMA using
native pointers:

    void *addr = malloc(N);
    set_dma_addr((uint64_t)addr);  // Pass user VA directly
    start_dma();

The device can now access 'addr' through the IOMMU's PASID-based translation,
provided that the underlying IOMMU hardware (e.g., Intel VT-d 3.1+, AMD-Vi,
ARM SMMU, RISCV IOMMU) and platform support SVA.

Dependencies:
- CONFIG_IOMMU_SVA must be enabled.
- The platform must support PRI (Page Request Interface) and PASID.
- Device drivers/userspace must handle page faults if demand-paging is used.

The implementation reuses core logic from uio_pci_generic.c while adding
PASID setting, and integration with the IOMMU SVA APIs.

Signed-off-by: Yaxing Guo <guoyaxing@bosc.ac.cn>
---
 drivers/uio/uio_pci_generic_sva.c | 188 ++++++++++++++++++++++++++++++
 1 file changed, 188 insertions(+)
 create mode 100644 drivers/uio/uio_pci_generic_sva.c

diff --git a/drivers/uio/uio_pci_generic_sva.c b/drivers/uio/uio_pci_generic_sva.c
new file mode 100644
index 000000000000..6a20c3487fed
--- /dev/null
+++ b/drivers/uio/uio_pci_generic_sva.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * UIO PCI Express sva driver
+ *
+ * Copyright (c) 2024 Beijing Institute of Open Source Chip (BOSC)
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/uio_driver.h>
+#include <linux/iommu.h>
+
+struct uio_pci_sva_dev {
+	struct pci_dev *pdev;
+	struct uio_info info;
+	struct iommu_sva *sva_handle;
+	int pasid;
+};
+
+static ssize_t pasid_show(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+	struct uio_pci_sva_dev *udev = pci_get_drvdata(pdev);
+
+	return sprintf(buf, "%d\n", udev->pasid);
+}
+static DEVICE_ATTR_RO(pasid);
+
+static irqreturn_t irq_handler(int irq, struct uio_info *dev_info)
+{
+	return IRQ_HANDLED;
+}
+
+static int uio_pci_sva_open(struct uio_info *info, struct inode *inode)
+{
+	struct iommu_sva *handle;
+	struct uio_pci_sva_dev *udev = info->priv;
+	struct iommu_domain *domain;
+
+	if (!udev && !udev->pdev)
+		return -ENODEV;
+
+	domain = iommu_get_domain_for_dev(&udev->pdev->dev);
+	if (domain)
+		iommu_detach_device(domain, &udev->pdev->dev);
+
+	handle = iommu_sva_bind_device(&udev->pdev->dev, current->mm);
+	if (IS_ERR(handle))
+		return -EINVAL;
+
+	udev->pasid = iommu_sva_get_pasid(handle);
+
+	udev->sva_handle = handle;
+
+	return 0;
+}
+
+static int uio_pci_sva_release(struct uio_info *info, struct inode *inode)
+{
+	struct uio_pci_sva_dev *udev = info->priv;
+	struct iommu_domain *domain;
+
+	if (!udev && !udev->pdev)
+		return -ENODEV;
+
+	domain = iommu_get_domain_for_dev(&udev->pdev->dev);
+	if (!domain)
+		return -ENODEV;
+
+	iommu_detach_device(domain, &udev->pdev->dev);
+
+	return 0;
+}
+
+static int probe(struct pci_dev *pdev, const struct pci_device_id *id)
+{
+	struct uio_pci_sva_dev *udev;
+	int ret, i, irq;
+
+	ret = pci_enable_device(pdev);
+	if (ret) {
+		dev_err(&pdev->dev, "pci_enable_device failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
+	if (ret)
+		goto out_disable;
+
+	pci_set_master(pdev);
+
+	ret = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_MSIX);
+	if (ret) {
+		irq = msi_get_virq(&pdev->dev, 0);
+		if (irq == -ENXIO)
+			ret = UIO_IRQ_NONE;
+		else if (irq < 0) {
+			ret = irq;
+			goto out_disable;
+		}
+	} else {
+		dev_warn(&pdev->dev, "Failed to allocate irq vectors\n");
+	}
+
+	udev = devm_kzalloc(&pdev->dev, sizeof(struct uio_pci_sva_dev),
+			    GFP_KERNEL);
+	if (!udev) {
+		ret =  -ENOMEM;
+		goto out_disable;
+	}
+
+	udev->pdev = pdev;
+	udev->info.name = "uio_pci_sva";
+	udev->info.version = "0.0.1";
+	udev->info.open = uio_pci_sva_open;
+	udev->info.release = uio_pci_sva_release;
+	udev->info.irq = irq;
+	udev->info.handler = irq_handler;
+	udev->info.priv = udev;
+
+	for (i = 0; i < MAX_UIO_MAPS; i++) {
+		struct resource *r = &pdev->resource[i];
+		struct uio_mem *uiomem = &udev->info.mem[i];
+
+		if (r->flags != (IORESOURCE_SIZEALIGN | IORESOURCE_MEM))
+			continue;
+
+		if (uiomem >= &udev->info.mem[MAX_UIO_MAPS]) {
+			dev_warn(&pdev->dev, "Do not support more than %d iomem\n",
+				 MAX_UIO_MAPS);
+			break;
+		}
+
+		uiomem->memtype = UIO_MEM_PHYS;
+		uiomem->addr = r->start & PAGE_MASK;
+		uiomem->offs = r->start & ~PAGE_MASK;
+		uiomem->size =
+			(uiomem->offs + resource_size(r) + PAGE_SIZE - 1) &
+			PAGE_MASK;
+		uiomem->name = r->name;
+	}
+
+	ret = sysfs_create_file(&pdev->dev.kobj, &dev_attr_pasid.attr);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to create sysfs file\n");
+		goto out_free;
+	}
+
+	ret = devm_uio_register_device(&pdev->dev, &udev->info);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register uio device\n");
+		goto out_rm_sysfs;
+	}
+
+	pci_set_drvdata(pdev, udev);
+
+	return 0;
+
+out_rm_sysfs:
+	sysfs_remove_file(&pdev->dev.kobj, &dev_attr_pasid.attr);
+out_free:
+	kfree(udev);
+out_disable:
+	pci_disable_device(pdev);
+
+	return ret;
+}
+
+static void remove(struct pci_dev *pdev)
+{
+	struct uio_info *info = pci_get_drvdata(pdev);
+
+	uio_unregister_device(info);
+	pci_release_regions(pdev);
+	pci_disable_device(pdev);
+}
+
+static struct pci_driver uio_pci_generic_sva_driver = {
+	.name = "uio_pci_sva",
+	.id_table = NULL,
+	.probe = probe,
+	.remove = remove,
+};
+
+module_pci_driver(uio_pci_generic_sva_driver);
+MODULE_LICENSE("GPL");
-- 
2.34.1

[RFC v1 2/2] uio: Add Kconfig and Makefile support for UIO_PCI_GENERIC_SVA

[Yaxing Guo]

Add config symbol and build infrastructure for the UIO PCI generic
driver with SVA (Shared Virtual Addressing) support.

This introduces:
- A new tristate config option 'UIO_PCI_GENERIC_SVA' in Kconfig,
  dependent on PCI and IOMMU_SVA.
- Build rule in Makefile to compile uio_pci_generic_sva.o when enabled.

Signed-off-by: Yaxing Guo <guoyaxing@bosc.ac.cn>
---
 drivers/uio/Kconfig  | 5 +++++
 drivers/uio/Makefile | 1 +
 2 files changed, 6 insertions(+)

diff --git a/drivers/uio/Kconfig b/drivers/uio/Kconfig
index b060dcd7c635..9849e53d1932 100644
--- a/drivers/uio/Kconfig
+++ b/drivers/uio/Kconfig
@@ -164,4 +164,9 @@ config UIO_DFL
 	    opae-sdk/tools/libopaeuio/
 
 	  If you compile this as a module, it will be called uio_dfl.
+
+config UIO_PCI_GENERIC_SVA
+	tristate "Generic driver for PCI Express that supports sva"
+	depends on PCI && IOMMU_SVA
+
 endif
diff --git a/drivers/uio/Makefile b/drivers/uio/Makefile
index 1c5f3b5a95cf..5352e21e918d 100644
--- a/drivers/uio/Makefile
+++ b/drivers/uio/Makefile
@@ -11,3 +11,4 @@ obj-$(CONFIG_UIO_MF624)         += uio_mf624.o
 obj-$(CONFIG_UIO_FSL_ELBC_GPCM)	+= uio_fsl_elbc_gpcm.o
 obj-$(CONFIG_UIO_HV_GENERIC)	+= uio_hv_generic.o
 obj-$(CONFIG_UIO_DFL)	+= uio_dfl.o
+obj-$(CONFIG_UIO_PCI_GENERIC_SVA)  += uio_pci_generic_sva.o
-- 
2.34.1

Re: [RFC v1 2/2] uio: Add Kconfig and Makefile support for UIO_PCI_GENERIC_SVA

[Greg KH]

On Thu, Sep 25, 2025 at 12:06:37PM +0800, Yaxing Guo wrote:
> Add config symbol and build infrastructure for the UIO PCI generic
> driver with SVA (Shared Virtual Addressing) support.
> 
> This introduces:
> - A new tristate config option 'UIO_PCI_GENERIC_SVA' in Kconfig,
>   dependent on PCI and IOMMU_SVA.
> - Build rule in Makefile to compile uio_pci_generic_sva.o when enabled.


This should be part of patch 1, no need to split this apart.

> Signed-off-by: Yaxing Guo <guoyaxing@bosc.ac.cn>
> ---
>  drivers/uio/Kconfig  | 5 +++++
>  drivers/uio/Makefile | 1 +
>  2 files changed, 6 insertions(+)
> 
> diff --git a/drivers/uio/Kconfig b/drivers/uio/Kconfig
> index b060dcd7c635..9849e53d1932 100644
> --- a/drivers/uio/Kconfig
> +++ b/drivers/uio/Kconfig
> @@ -164,4 +164,9 @@ config UIO_DFL
>  	    opae-sdk/tools/libopaeuio/
>  
>  	  If you compile this as a module, it will be called uio_dfl.
> +
> +config UIO_PCI_GENERIC_SVA
> +	tristate "Generic driver for PCI Express that supports sva"
> +	depends on PCI && IOMMU_SVA
> +

Please provide more information here, like the other entries have.

thanks,

greg k-h

Re: [RFC v1 1/2] uio: Add SVA support for PCI devices via uio_pci_generic_sva.c

[Greg KH]

On Thu, Sep 25, 2025 at 12:06:36PM +0800, Yaxing Guo wrote:
> This patch introduces a new UIO driver, uio_pci_generic_sva, which
> extends the functionality of uio_pci_generic by adding support for
> Shared Virtual Addressing (SVA) when IOMMU is enabled in the system.
> 
> The key enhancement allows PCI devices to directly use user-space virtual
> addresses for DMA operations, eliminating the need for bounce buffers or
> explicit IOVA mapping. This is achieved by leveraging the kernel's IOMMU-SVA
> subsystem, including process address space attachment, page fault handling,
> and shared context management between CPU and device.
> 
> With this driver, userspace applications can perform zero-copy DMA using
> native pointers:
> 
>     void *addr = malloc(N);
>     set_dma_addr((uint64_t)addr);  // Pass user VA directly
>     start_dma();
> 
> The device can now access 'addr' through the IOMMU's PASID-based translation,
> provided that the underlying IOMMU hardware (e.g., Intel VT-d 3.1+, AMD-Vi,
> ARM SMMU, RISCV IOMMU) and platform support SVA.
> 
> Dependencies:
> - CONFIG_IOMMU_SVA must be enabled.
> - The platform must support PRI (Page Request Interface) and PASID.
> - Device drivers/userspace must handle page faults if demand-paging is used.
> 
> The implementation reuses core logic from uio_pci_generic.c while adding
> PASID setting, and integration with the IOMMU SVA APIs.
> 
> Signed-off-by: Yaxing Guo <guoyaxing@bosc.ac.cn>
> ---
>  drivers/uio/uio_pci_generic_sva.c | 188 ++++++++++++++++++++++++++++++
>  1 file changed, 188 insertions(+)
>  create mode 100644 drivers/uio/uio_pci_generic_sva.c
> 
> diff --git a/drivers/uio/uio_pci_generic_sva.c b/drivers/uio/uio_pci_generic_sva.c
> new file mode 100644
> index 000000000000..6a20c3487fed
> --- /dev/null
> +++ b/drivers/uio/uio_pci_generic_sva.c
> @@ -0,0 +1,188 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * UIO PCI Express sva driver
> + *
> + * Copyright (c) 2024 Beijing Institute of Open Source Chip (BOSC)

It is now 2025 :)


> + */
> +
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/uio_driver.h>
> +#include <linux/iommu.h>
> +
> +struct uio_pci_sva_dev {
> +	struct pci_dev *pdev;
> +	struct uio_info info;
> +	struct iommu_sva *sva_handle;
> +	int pasid;
> +};
> +
> +static ssize_t pasid_show(struct device *dev,
> +			  struct device_attribute *attr, char *buf)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	struct uio_pci_sva_dev *udev = pci_get_drvdata(pdev);
> +
> +	return sprintf(buf, "%d\n", udev->pasid);

sysfs_emit() please.

> +}
> +static DEVICE_ATTR_RO(pasid);

All sysfs attributes need to be documented in Documentation/ABI/

> +static int probe(struct pci_dev *pdev, const struct pci_device_id *id)
> +{
> +	struct uio_pci_sva_dev *udev;
> +	int ret, i, irq;
> +
> +	ret = pci_enable_device(pdev);
> +	if (ret) {
> +		dev_err(&pdev->dev, "pci_enable_device failed: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
> +	if (ret)
> +		goto out_disable;
> +
> +	pci_set_master(pdev);
> +
> +	ret = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_MSIX);
> +	if (ret) {
> +		irq = msi_get_virq(&pdev->dev, 0);
> +		if (irq == -ENXIO)
> +			ret = UIO_IRQ_NONE;
> +		else if (irq < 0) {
> +			ret = irq;
> +			goto out_disable;
> +		}
> +	} else {
> +		dev_warn(&pdev->dev, "Failed to allocate irq vectors\n");

Why doesn't this fail probe?

> +	}
> +
> +	udev = devm_kzalloc(&pdev->dev, sizeof(struct uio_pci_sva_dev),
> +			    GFP_KERNEL);
> +	if (!udev) {
> +		ret =  -ENOMEM;
> +		goto out_disable;
> +	}
> +
> +	udev->pdev = pdev;
> +	udev->info.name = "uio_pci_sva";
> +	udev->info.version = "0.0.1";
> +	udev->info.open = uio_pci_sva_open;
> +	udev->info.release = uio_pci_sva_release;
> +	udev->info.irq = irq;
> +	udev->info.handler = irq_handler;
> +	udev->info.priv = udev;
> +
> +	for (i = 0; i < MAX_UIO_MAPS; i++) {
> +		struct resource *r = &pdev->resource[i];
> +		struct uio_mem *uiomem = &udev->info.mem[i];
> +
> +		if (r->flags != (IORESOURCE_SIZEALIGN | IORESOURCE_MEM))
> +			continue;
> +
> +		if (uiomem >= &udev->info.mem[MAX_UIO_MAPS]) {
> +			dev_warn(&pdev->dev, "Do not support more than %d iomem\n",
> +				 MAX_UIO_MAPS);
> +			break;
> +		}
> +
> +		uiomem->memtype = UIO_MEM_PHYS;
> +		uiomem->addr = r->start & PAGE_MASK;
> +		uiomem->offs = r->start & ~PAGE_MASK;
> +		uiomem->size =
> +			(uiomem->offs + resource_size(r) + PAGE_SIZE - 1) &
> +			PAGE_MASK;
> +		uiomem->name = r->name;
> +	}
> +
> +	ret = sysfs_create_file(&pdev->dev.kobj, &dev_attr_pasid.attr);

You just raced with userspace and lost.  Please use the default
attribute list instead.

> +module_pci_driver(uio_pci_generic_sva_driver);
> +MODULE_LICENSE("GPL");

You now also need a MODULE_DESCRIPTION(), didn't you get a build warning
without it?

thanks,

greg k-h