SNAP-4 Service Release Notes

Workaround: Ignore the value and assume the free_queues pool is large enough.

Description: The SPDK bdev_uring is not supported. It will be supported next release.

Workaround: N/A

3689918

3753637

3985953

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Description: Some old Windows OS NVMe drivers have buggy usage of SGL support.

Workaround: Disable SGL support when using Windows OS by setting the --quirks bit 4 to 1 in snap_rpc.py nvme_controller_create RPC.

Keywords: Windows; NVMe

Reported in version: 4.4.0

2879262

Description: When the virtio-blk kernel driver cannot find enough MSI-X vectors to satisfy all its opened virtqueues, it failovers to assign a single MSI-X vector to all virtqueues which negatively impacts performance. In addition, when a large number (e.g., 64) of virtqueues are associated with a single MSI-X, the kernel may enter a soft-lockup (kernel bug) and the IO will hang.

Workaround: Always keep num_queues < num_msix. Best practice is to not set --num_queues at all when creating virtio-blk controllers, and the best-suited value is automatically chosen based on available MSI-X.

Keywords: Virtio-blk; kernel driver; MSI-X

Reported in version: 4.3.0

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Description: If PCIe devices are inserted prior to the hot-plug driver being loaded on host, the hot-plug driver in kernel version less than 4.19 does not enable the slot even if the slot is occupied (i.e., presence detected in slot status register). That is, only the presence state of the slot is changed by firmware but the PCIe slot is not enabled by the kernel after host bootup (i.e.,

So that we can't get the PCIe device by lspci on host side, and the bdf is 0 on controller.

Workaround: Add pciehp.pciehp_force=1 to the boot command line on host.

Keywords: Virtio-blk; kernel driver; hot-plug

Reported in version: 4.2.1

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Description: RedHat/Centos 7.x does not handle "online" (post driver probe) namespace additions/removals correctly.

Workaround: Use --quirks=0x2 option in snap_rpc.py nvme_controller_create.

Keywords: NVMe; CentOS; RedHat; kernel

Reported in version: 4.1.0

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Description: Some Windows drivers have experimental support for "online" (post driver probe) namespace additions/removal, although such support is not communicated with the device.

Workaround: Use --quirks=0x1 option in snap_rpc.py nvme_controller_create.

Keywords: NVMe; Windows

Reported in version: 4.1.0

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Description: VMWare ESXi supports "online" (post driver probe) namespace additions/removal, only if “Namespace Management” is supported by controller.

Workaround: Use --quirks=0x8 option in snap_rpc.py nvme_controller_create.

Keywords: NVMe, ESXi

Reported in version: 4.1.0

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Description: Ubuntu 22.04 does not support 500 VFs.

Workaround: N/A

Keywords: Virtio-blk; kernel driver; Ubuntu 22.04

Reported in version: 4.1.0

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Description: Virtio-blk Linux kernel driver does not handle PCIe FLR events.

Workaround: N/A

Keywords: Virtio-blk; kernel driver

Reported in version: 4.0.0

3679373

Description: Virtio-blk spdk driver (vfio-pci based) does not handle PCIe FLR events.

Workaround: N/A

Keywords: Virtio-blk; SPDK driver

Reported in version: 4.3.0

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Description: A n ew virtio-blk Linux kernel driver (starting kernel 4.18) does not support hot-unplug during traffic. Since the kernel may self-generate spontaneous IOs, on rare occasions, an issue may happen even when no traffic is explicitly being run.

Workaround: N/A

Keywords: Virtio-blk; kernel driver

Reported in version: 4.0.0

Description: SPDK NVMf/RDMA initiator fails to connect to kernel NVMf/RDMA remote target.

Workaround: Use setting spdk_rpc.py bdev_nvme_set_options --io-queue-requests=128 on SPDK configuration

Keywords: SPDK, NVMf, RDMA, kernel

Reported in version: 4.3.1

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Description: Windows OS virtio-blk driver expects at least 64K data to be available for a single IO request

Workaround: Use seg_max and size_max parameters configuration to match requirements (`seg_max * size_max > 64K`).

Keywords: Windows, virtio-blk

Reported in version: 4.3.1

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Description: Some old Windows OS versions have malfunctioning inbox virtio-blk driver, expects a 3-party virtio-blk driver to be pre-installed to operate properly.

Workaround: Use verified 3-party driver published by fedora (link).

Keywords: Windows, virtio-blk

Reported in version: 4.3.1

4184299

Description: When using hotplugged PCIe devices, host OS can't detect PCIe changes during runtime - it can only do it during booting stage.

Workaround: In hotplug scenario - after all desired new devices are plugged - OS must be rebooted. In hotunplug scenario - after every existing device that is removed - OS must be rebooted (some Windows versions will perform reboot automatically).

Keywords: Hotplug, Windows.

Reported in version: 4.5.0

3748674

Description: On most modern Linux Distributions - Unplugging a PCIe function from the host while there are still inflight IOs on it, will cause virtio-blk driver to hang.

Workaround: N/A

Keywords: Hotplug, Linux.

Reported in version: 4.5.0