This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- xenial' to 'verification-done-xenial'. If the problem still exists, change the tag 'verification-needed-xenial' to 'verification-failed- xenial'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-xenial ** Tags added: verification-needed-yakkety -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1661430 Title: [Hyper-V] Fix ring buffer handling to avoid host throttling Status in linux package in Ubuntu: Fix Committed Status in linux source package in Xenial: Fix Committed Status in linux source package in Yakkety: Fix Committed Status in linux source package in Zesty: Fix Committed Bug description: An unfortunate side effect of some of the recent work done to improve ring buffer performance made a situation where the host would interpret guest requests as a denial of service attack, pausing guest communications for five seconds. This series of fixes corrects this problem. Needed for each kernel that has included a389fcfd2cb5 ("Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read()") https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=74198eb4a42c4a3c4fbef08fa01a291a282f7c2e Drivers: hv: vmbus: Base host signaling strictly on the ring state One of the factors that can result in the host concluding that a given guest in mounting a DOS attack is if the guest generates interrupts to the host when the host is not expecting it. If these "spurious" interrupts reach a certain rate, the host can throttle the guest to minimize the impact. The host computation of the "expected number of interrupts" is strictly based on the ring transitions. Until the host logic is fixed, base the guest logic to interrupt solely on the ring state. https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1f6ee4e7d83586c8b10bd4f2f4346353d04ce884 Drivers: hv: vmbus: On write cleanup the logic to interrupt the host Signal the host when we determine the host is to be signaled. The currrent code determines the need to signal in the ringbuffer code and actually issues the signal elsewhere. This can result in the host viewing this interrupt as spurious since the host may also poll the channel. Make the necessary adjustments. https://git.kernel.org/cgit/linux/kernel/git/next/linux- next.git/commit/?id=3372592a140db69fd63837e81f048ab4abf8111e Drivers: hv: vmbus: On the read path cleanup the logic to interrupt the host Signal the host when we determine the host is to be signaled - on th read path. The currrent code determines the need to signal in the ringbuffer code and actually issues the signal elsewhere. This can result in the host viewing this interrupt as spurious since the host may also poll the channel. Make the necessary adjustments. https://git.kernel.org/cgit/linux/kernel/git/next/linux- next.git/commit/?id=433e19cf33d34bb6751c874a9c00980552fe508c Drivers: hv: vmbus: finally fix hv_need_to_signal_on_read() Commit a389fcfd2cb5 ("Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read()") added the proper mb(), but removed the test "prev_write_sz < pending_sz" when making the signal decision. As a result, the guest can signal the host unnecessarily, and then the host can throttle the guest because the host thinks the guest is buggy or malicious; finally the user running stress test can perceive intermittent freeze of the guest. This patch brings back the test, and properly handles the in-place consumption APIs used by NetVSC (see get_next_pkt_raw(), put_pkt_raw() and commit_rd_index()). Fixes: a389fcfd2cb5 ("Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read()") To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1661430/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
