PCI: hv: Add hibernation support
Add suspend() and resume() functions so that Hyper-V virtual PCI devices are handled properly when the VM hibernates and resumes from hibernation. Note that the suspend() function must make sure there are no pending work items before calling vmbus_close(), since it runs in a process context as a callback in dpm_suspend(). When it starts to run, the channel callback hv_pci_onchannelcallback(), which runs in a tasklet context, can be still running concurrently and scheduling new work items onto hbus->wq in hv_pci_devices_present() and hv_pci_eject_device(), and the work item handlers can access the vmbus channel, which can be being closed by hv_pci_suspend(), e.g. the work item handler pci_devices_present_work() -> new_pcichild_device() writes to the vmbus channel. To eliminate the race, hv_pci_suspend() disables the channel callback tasklet, sets hbus->state to hv_pcibus_removing, and re-enables the tasklet. This way, when hv_pci_suspend() proceeds, it knows that no new work item can be scheduled, and then it flushes hbus->wq and safely closes the vmbus channel. Signed-off-by:Dexuan Cui <decui@microsoft.com> Signed-off-by:
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Reviewed-by:
Michael Kelley <mikelley@microsoft.com>
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