This is part 2 for the vfio-pci driver power management support. Part 1 of this patch series was related to adding D3cold support when there is no user of the VFIO device and has already merged in the mainline kernel. If we enable the runtime power management for vfio-pci device in the guest OS, then the device is being runtime suspended (for linux guest OS) and the PCI device will be put into D3hot state (in function vfio_pm_config_write()). If the D3cold state can be used instead of D3hot, then it will help in saving maximum power. The D3cold state can't be possible with native PCI PM. It requires interaction with platform firmware which is system-specific. To go into low power states (Including D3cold), the runtime PM framework can be used which internally interacts with PCI and platform firmware and puts the device into the lowest possible D-States. This patch series adds the support to engage runtime power management initiated by the user. Since D3cold state can't be achieved by writing PCI standard PM config registers, so new device features have been added in DEVICE_FEATURE IOCTL for low power entry and exit related handling. For the PCI device, this low power state will be D3cold (if the platform supports the D3cold state). The hypervisors can implement virtual ACPI methods to make the integration with guest OS. For example, in guest Linux OS if PCI device ACPI node has _PR3 and _PR0 power resources with _ON/_OFF method, then guest Linux OS makes the _OFF call during D3cold transition and then _ON during D0 transition. The hypervisor can tap these virtual ACPI calls and then do the low power related IOCTL. The entry device feature has two variants. These two variants are mainly to support the different behaviour for the low power entry. If there is any access for the VFIO device on the host side, then the device will be moved out of the low power state without the user's guest driver involvement. Some devices (for example NVIDIA VGA or 3D controller) require the user's guest driver involvement for each low-power entry. In the first variant, the host can move the device into low power without any guest driver involvement while in the second variant, the host will send a notification to user through eventfd and then user guest driver needs to move the device into low power. The hypervisor can implement the virtual PME support to notify the guest OS. Please refer https://lore.kernel.org/lkml/20220701110814.7310-7-abhsahu@xxxxxxxxxx/ where initially this virtual PME was implemented in the vfio-pci driver itself, but later-on, it has been decided that hypervisor can implement this. * Changes in v5 - Rebased patches on https://github.com/awilliam/linux-vfio/tree/next. - Implemented 3 separate device features for the low power entry and exit. - Dropped virtual PME patch. - Removed the special handling for power management related device feature and now all the ioctls will be wrapped under pm_runtime_get/put. - Refactored code around low power entry and exit. - Removed all the policy related code and same can be implemented in the userspace. - Renamed 'intx_masked' to 'masked_changed' and updated function comment. - Changed the order of patches. * Changes in v4 (https://lore.kernel.org/lkml/20220701110814.7310-1-abhsahu@xxxxxxxxxx/) - Rebased patches on v5.19-rc4. - Added virtual PME support. - Used flags for low power entry and exit instead of explicit variable. - Add the support to keep NVIDIA display related controllers in active state if there is any activity on the host side. - Add a flag that can be set by the user to keep the device in the active state if there is any activity on the host side. - Split the D3cold patch into smaller patches. - Kept the runtime PM usage count incremented for all the IOCTL (except power management IOCTL) and all the PCI region access. - Masked the runtime errors behind -EIO. - Refactored logic in runtime suspend/resume routine and for power management device feature IOCTL. - Add helper function for pm_runtime_put() also in the drivers/vfio/vfio.c and use the 'struct vfio_device' for the function parameter. - Removed the requirement to move the device into D3hot before calling low power entry. - Renamed power management related new members in the structure. - Used 'pm_runtime_engaged' check in __vfio_pci_memory_enabled(). * Changes in v3 (https://lore.kernel.org/lkml/20220425092615.10133-1-abhsahu@xxxxxxxxxx) - Rebased patches on v5.18-rc3. - Marked this series as PATCH instead of RFC. - Addressed the review comments given in v2. - Removed the limitation to keep device in D0 state if there is any access from host side. This is specific to NVIDIA use case and will be handled separately. - Used the existing DEVICE_FEATURE IOCTL itself instead of adding new IOCTL for power management. - Removed all custom code related with power management in runtime suspend/resume callbacks and IOCTL handling. Now, the callbacks contain code related with INTx handling and few other stuffs and all the PCI state and platform PM handling will be done by PCI core functions itself. - Add the support of wake-up in main vfio layer itself since now we have more vfio/pci based drivers. - Instead of assigning the 'struct dev_pm_ops' in individual parent driver, now the vfio_pci_core tself assigns the 'struct dev_pm_ops'. - Added handling of power management around SR-IOV handling. - Moved the setting of drvdata in a separate patch. - Masked INTx before during runtime suspended state. - Changed the order of patches so that Fix related things are at beginning of this patch series. - Removed storing the power state locally and used one new boolean to track the d3 (D3cold and D3hot) power state - Removed check for IO access in D3 power state. - Used another helper function vfio_lock_and_set_power_state() instead of touching vfio_pci_set_power_state(). - Considered the fixes made in https://lore.kernel.org/lkml/20220217122107.22434-1-abhsahu@xxxxxxxxxx and updated the patches accordingly. * Changes in v2 (https://lore.kernel.org/lkml/20220124181726.19174-1-abhsahu@xxxxxxxxxx) - Rebased patches on v5.17-rc1. - Included the patch to handle BAR access in D3cold. - Included the patch to fix memory leak. - Made a separate IOCTL that can be used to change the power state from D3hot to D3cold and D3cold to D0. - Addressed the review comments given in v1. * v1 (https://lore.kernel.org/lkml/20211115133640.2231-1-abhsahu@xxxxxxxxxx) Abhishek Sahu (5): vfio: Add the device features for the low power entry and exit vfio: Increment the runtime PM usage count during IOCTL call vfio/pci: Mask INTx during runtime suspend vfio/pci: Implement VFIO_DEVICE_FEATURE_LOW_POWER_ENTRY/EXIT vfio/pci: Implement VFIO_DEVICE_FEATURE_LOW_POWER_ENTRY_WITH_WAKEUP drivers/vfio/pci/vfio_pci_core.c | 256 ++++++++++++++++++++++++++++-- drivers/vfio/pci/vfio_pci_intrs.c | 6 +- drivers/vfio/vfio.c | 52 +++++- include/linux/vfio_pci_core.h | 5 +- include/uapi/linux/vfio.h | 55 +++++++ 5 files changed, 357 insertions(+), 17 deletions(-) -- 2.17.1
