After VM requests for channel offers during boot or resume from hibernation, host offers the devices that the VM is configured with and then sends a separate message indicating that all the boot-time channel offers are delivered. Wait for this message to make this boot-time offers request and receipt process synchronous. Without this, user mode can race with VMBus initialization and miss channel offers. User mode has no way to work around this other than sleeping for a while, since there is no way to know when VMBus has finished processing boot-time offers. This is in analogy to a PCI bus not returning from probe until it has scanned all devices on the bus. As part of this implementation, some code cleanup is also done for the logic which becomes redundant due to this change. Second patch prints the channels which are not offered when resume happens from hibernation to supply more information to the end user. Changes since v2: https://lore.kernel.org/all/20241029080147.52749-1-namjain@xxxxxxxxxxxxxxxxxxx/ * Incorporated Easwar's suggestion to use secs_to_jiffies() as his changes are now merged. * Addressed Michael's comments: * Used boot-time offers/channels/devices to maintain consistency * Rephrased CHANNELMSG_ALLOFFERS_DELIVERED handler function comments for better explanation. Thanks for sharing the write-up. * Changed commit msg and other things as per suggestions * Addressed Dexuan's comments, which came up in offline discussion: * Changed timeout for waiting for all offers delivered msg to 60s instead of 10s. Reason being, the host can experience some servicing events or diagnostics events, which may take a long time and hence may fail to offer all the devices within 10s. * Minor additions in commit subject of both patches * Rebased on latest linux-next master tip Changes since v1: https://lore.kernel.org/all/20241018115811.5530-1-namjain@xxxxxxxxxxxxxxxxxxx/ * Added Easwar's Reviewed-By tag * Addressed Michael's comments: * Added explanation of all offers delivered message in comments * Removed infinite wait for offers logic, and changed it wait once. * Removed sub channel workqueue flush logic * Added comments on why MLX device offer is not expected as part of this essential boot offer list. I refrained from adding too many details on it as it felt like it is beyond the scope of this patch series and may not be relevant to this. However, please let me know if something needs to be added. * Addressed Saurabh's comments: * Changed timeout value to 10000 ms instead of 10*1000 * Changed commit msg as per suggestions * Added a comment for warning case of wait_for_completion timeout * Added a note for missing channel cleanup in comments and commit msg John Starks (1): Drivers: hv: vmbus: Log on missing offers if any Naman Jain (1): Drivers: hv: vmbus: Wait for boot-time offers during boot and resume drivers/hv/channel_mgmt.c | 61 +++++++++++++++++++++++++++++---------- drivers/hv/connection.c | 4 +-- drivers/hv/hyperv_vmbus.h | 14 ++------- drivers/hv/vmbus_drv.c | 31 ++++++++++---------- 4 files changed, 67 insertions(+), 43 deletions(-) base-commit: 28955f4fa2823e39f1ecfb3a37a364563527afbc -- 2.34.1
