vduse: Introduce VDUSE - vDPA Device in Userspace

This VDUSE driver enables implementing software-emulated vDPA devices in userspace. The vDPA device is created by ioctl(VDUSE_CREATE_DEV) on /dev/vduse/control. Then a char device interface (/dev/vduse/$NAME) is exported to userspace for device emulation. In order to make the device emulation more secure, the device's control path is handled in kernel. A message mechnism is introduced to forward some dataplane related control messages to userspace. And in the data path, the DMA buffer will be mapped into userspace address space through different ways depending on the vDPA bus to which the vDPA device is attached. In virtio-vdpa case, the MMU-based software IOTLB is used to achieve that. And in vhost-vdpa case, the DMA buffer is reside in a userspace memory region which can be shared to the VDUSE userspace processs via transferring the shmfd. For more details on VDUSE design and usage, please see the follow-on Documentation commit. NB(mst): when merging this with b542e38 ("eventfd: Make signal recursion protection a task bit") replace eventfd_signal_count with eventfd_signal_allowed, and drop the previous ("eventfd: Export eventfd_wake_count to modules"). Signed-off-by: Xie Yongji <[email protected]> Acked-by: Jason Wang <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Michael S. Tsirkin <[email protected]>
ashr · Sep 6, 2021 · c8a6153 · c8a6153
1 parent 8c773d5
commit c8a6153
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diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -300,6 +300,7 @@ Code  Seq#    Include File                                           Comments
 'z'   10-4F  drivers/s390/crypto/zcrypt_api.h                        conflict!
 '|'   00-7F  linux/media.h
 0x80  00-1F  linux/fb.h
+0x81  00-1F  linux/vduse.h
 0x89  00-06  arch/x86/include/asm/sockios.h
 0x89  0B-DF  linux/sockios.h
 0x89  E0-EF  linux/sockios.h                                         SIOCPROTOPRIVATE range

diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
@@ -33,6 +33,16 @@ config VDPA_SIM_BLOCK
 	  vDPA block device simulator which terminates IO request in a
 	  memory buffer.
 
+config VDPA_USER
+	tristate "VDUSE (vDPA Device in Userspace) support"
+	depends on EVENTFD && MMU && HAS_DMA
+	select DMA_OPS
+	select VHOST_IOTLB
+	select IOMMU_IOVA
+	help
+	  With VDUSE it is possible to emulate a vDPA Device
+	  in a userspace program.
+
 config IFCVF
 	tristate "Intel IFC VF vDPA driver"
 	depends on PCI_MSI

diff --git a/drivers/vdpa/Makefile b/drivers/vdpa/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_VDPA) += vdpa.o
 obj-$(CONFIG_VDPA_SIM) += vdpa_sim/
+obj-$(CONFIG_VDPA_USER) += vdpa_user/
 obj-$(CONFIG_IFCVF)    += ifcvf/
 obj-$(CONFIG_MLX5_VDPA) += mlx5/
 obj-$(CONFIG_VP_VDPA)    += virtio_pci/
diff --git a/drivers/vdpa/vdpa_user/Makefile b/drivers/vdpa/vdpa_user/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+vduse-y := vduse_dev.o iova_domain.o
+
+obj-$(CONFIG_VDPA_USER) += vduse.o