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Without memory barrier, the change of used ring index could not immediately detected by FE, this would bring some problems. For virtio-blk FE driver, when it receives an interrupt, and confirms the used ring index has changed, it will first set ring flags with VRING_AVAIL_F_NO_INTERRUPT, then get buffer from virtqueue, after process this request, it will mask VRING_AVAIL_F_NO_INTERRUPT, and get used ring index again before return. If used ring changes, it will process it. At the same time, BE will read this flags before each notify, if VRING_AVAIL_F_NO_INTERRUPT was set, BE will not inject interrupt. Without memory barrier, before FE mask VRING_AVAIL_F_NO_INTERRUPT, BE has finished notify without interrupt, then FE mask VRING_AVAIL_F_NO_INTERRUPT, and get used ring index but failed (index has changed from BE side). FE will return from interrupt handler function, and wait for next interrupt which was not injected by BE. Thus, this will cause kernel hung. Tracked-On: #2628 Signed-off-by: Conghui Chen <conghui.chen@intel.com> Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
ACRN Device Model ################# Introduction ============ The ACRN Device Model provides **device sharing** capabilities between the Service OS and Guest OSs. It is a component that is used in conjunction with the `ACRN Hypervisor`_ and this is installed within the Service OS. You can find out more about Project ACRN on the `Project ACRN documentation`_ website. .. _`ACRN Hypervisor`: https://github.com/projectacrn/acrn-hypervisor .. _`Project ACRN documentation`: https://projectacrn.github.io/