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4813724c4b
This patch adds INTx handling during runtime suspend/resume. All the suspend/resume related code for the user to put the device into the low power state will be added in subsequent patches. The INTx lines may be shared among devices. Whenever any INTx interrupt comes for the VFIO devices, then vfio_intx_handler() will be called for each device sharing the interrupt. Inside vfio_intx_handler(), it calls pci_check_and_mask_intx() and checks if the interrupt has been generated for the current device. Now, if the device is already in the D3cold state, then the config space can not be read. Attempt to read config space in D3cold state can cause system unresponsiveness in a few systems. To prevent this, mask INTx in runtime suspend callback, and unmask the same in runtime resume callback. If INTx has been already masked, then no handling is needed in runtime suspend/resume callbacks. 'pm_intx_masked' tracks this, and vfio_pci_intx_mask() has been updated to return true if the INTx vfio_pci_irq_ctx.masked value is changed inside this function. For the runtime suspend which is triggered for the no user of VFIO device, the 'irq_type' will be VFIO_PCI_NUM_IRQS and these callbacks won't do anything. The MSI/MSI-X are not shared so similar handling should not be needed for MSI/MSI-X. vfio_msihandler() triggers eventfd_signal() without doing any device-specific config access. When the user performs any config access or IOCTL after receiving the eventfd notification, then the device will be moved to the D0 state first before servicing any request. Another option was to check this flag 'pm_intx_masked' inside vfio_intx_handler() instead of masking the interrupts. This flag is being set inside the runtime_suspend callback but the device can be in non-D3cold state (for example, if the user has disabled D3cold explicitly by sysfs, the D3cold is not supported in the platform, etc.). Also, in D3cold supported case, the device will be in D0 till the PCI core moves the device into D3cold. In this case, there is a possibility that the device can generate an interrupt. Adding check in the IRQ handler will not clear the IRQ status and the interrupt line will still be asserted. This can cause interrupt flooding. Signed-off-by: Abhishek Sahu <abhsahu@nvidia.com> Link: https://lore.kernel.org/r/20220829114850.4341-4-abhsahu@nvidia.com Signed-off-by: Alex Williamson <alex.williamson@redhat.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.