> From: Alex Williamson <alex.williamson@xxxxxxxxxx> > Sent: Tuesday, February 14, 2023 11:47 PM > > On Tue, 14 Feb 2023 01:55:17 +0000 > "Liu, Yi L" <yi.l.liu@xxxxxxxxx> wrote: > > > > From: Alex Williamson <alex.williamson@xxxxxxxxxx> > > > Sent: Tuesday, February 14, 2023 3:47 AM > > > > > > On Mon, 13 Feb 2023 07:13:33 -0800 > > > Yi Liu <yi.l.liu@xxxxxxxxx> wrote: > > > > > > > Existing VFIO provides group-centric user APIs for userspace. > Userspace > > > > opens the /dev/vfio/$group_id first before getting device fd and > hence > > > > getting access to device. This is not the desired model for iommufd. > Per > > > > the conclusion of community discussion[1], iommufd provides device- > > > centric > > > > kAPIs and requires its consumer (like VFIO) to be device-centric user > > > > APIs. Such user APIs are used to associate device with iommufd and > also > > > > the I/O address spaces managed by the iommufd. > > > > > > > > This series first introduces a per device file structure to be prepared > > > > for further enhancement and refactors the kvm-vfio code to be > prepared > > > > for accepting device file from userspace. Then refactors the vfio to be > > > > able to handle iommufd binding. This refactor includes the mechanism > of > > > > blocking device access before iommufd bind, making > vfio_device_open() > > > be > > > > exclusive between the group path and the cdev path. Eventually, adds > the > > > > cdev support for vfio device, and makes group infrastructure optional > as > > > > it is not needed when vfio device cdev is compiled. > > > > > > > > This is also a prerequisite for iommu nesting for vfio device[2]. > > > > > > > > The complete code can be found in below branch, simple test done > with > > > the > > > > legacy group path and the cdev path. Draft QEMU branch can be found > > > at[3] > > > > > > > > https://github.com/yiliu1765/iommufd/tree/vfio_device_cdev_v3 > > > > (config CONFIG_IOMMUFD=y CONFIG_VFIO_DEVICE_CDEV=y) > > > > > > Even using your branch[1], it seems like this has not been tested > > > except with cdev support enabled: > > > > > > /home/alwillia/Work/linux.git/drivers/vfio/vfio_main.c: In function > > > ‘vfio_device_add’: > > > /home/alwillia/Work/linux.git/drivers/vfio/vfio_main.c:253:48: error: > ‘struct > > > vfio_device’ has no member named ‘cdev’; did you mean ‘dev’? > > > 253 | ret = cdev_device_add(&device->cdev, &device->device); > > > | ^~~~ > > > | dev > > > /home/alwillia/Work/linux.git/drivers/vfio/vfio_main.c: In function > > > ‘vfio_device_del’: > > > /home/alwillia/Work/linux.git/drivers/vfio/vfio_main.c:262:42: error: > ‘struct > > > vfio_device’ has no member named ‘cdev’; did you mean ‘dev’? > > > 262 | cdev_device_del(&device->cdev, &device->device); > > > | ^~~~ > > > | dev > > > > Sorry for it. It is due to the cdev definition is under > > "#if IS_ENABLED(CONFIG_VFIO_DEVICE_CDEV)". While, in the code it > > uses "if (IS_ENABLED(CONFIG_VFIO_DEVICE_CDEV))". I think for > > readability, it would be better to always define cdev in vfio_device, > > and keep the using of cdev in code. How about your taste? > > It seems necessary unless we want to litter the code with #ifdefs. I've moved it to the header file and call cdev_device_add() under #if (IS_ENABLED(CONFIG_VFIO_DEVICE_CDEV))". > > > Additionally the VFIO_ENABLE_GROUP Kconfig option doesn't make much > > > sense to me, it seems entirely redundant to VFIO_GROUP. > > > > The intention is to make the group code compiling match existing case. > > Currently, if VFIO is configured, group code is by default compiled. > > So VFIO_ENABLE_GROUP a hidden option, and VFIO_GROUP an option > > for user. User needs to explicitly config VFIO_GROUP if VFIO_DEVICE_CDEV==y. > > If VFIO_DEVICE_CDEV==n, then no matter user configed VFIO_GROUP or > > not, the group code shall be compiled. > > I understand the mechanics, I still find VFIO_ENABLE_GROUP redundant > and unnecessary. Also, Kconfig should not allow a configuration > without either VFIO_GROUP or VFIO_DEVICE_CDEV as this is not > functional. Deselecting VFIO_GROUP should select VFIO_DEVICE_CDEV, > but VFIO_DEVICE_CDEV should be an optional addition to VFIO_GROUP. How about below? As Jason's remark on patch 0003, cdev is not available for SPAPR. diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig index 0476abf154f2..96535adc2301 100644 --- a/drivers/vfio/Kconfig +++ b/drivers/vfio/Kconfig @@ -4,6 +4,8 @@ menuconfig VFIO select IOMMU_API depends on IOMMUFD || !IOMMUFD select INTERVAL_TREE + select VFIO_GROUP if SPAPR_TCE_IOMMU + select VFIO_DEVICE_CDEV if !VFIO_GROUP && (X86 || S390 || ARM || ARM64) select VFIO_CONTAINER if IOMMUFD=n help VFIO provides a framework for secure userspace device drivers. @@ -14,7 +16,8 @@ menuconfig VFIO if VFIO config VFIO_DEVICE_CDEV bool "Support for the VFIO cdev /dev/vfio/devices/vfioX" depends on IOMMUFD && (X86 || S390 || ARM || ARM64) + default !VFIO_GROUP help The VFIO device cdev is another way for userspace to get device access. Userspace gets device fd by opening device cdev under @@ -23,9 +26,21 @@ config VFIO_DEVICE_CDEV If you don't know what to do here, say N. +config VFIO_GROUP + bool "Support for the VFIO group /dev/vfio/$group_id" + default y + help + VFIO group is legacy interface for userspace. As the introduction + of VFIO device cdev interface, this can be N. For now, before + userspace applications are fully converted to new vfio device cdev + interface, this should be Y. + + If you don't know what to do here, say Y. + config VFIO_CONTAINER bool "Support for the VFIO container /dev/vfio/vfio" select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64) + depends on VFIO_GROUP default y help The VFIO container is the classic interface to VFIO for establishing Regards, Yi Liu
