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Update to Network Channel count calculation in test case 'verify_vmbus_devices_channels' #3644

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Update to Network Channel count calculation in test case 'verify_vmbus_devices_channels' #3644

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c3150b3
using ethtool to get the expected channel count
umfranci Feb 11, 2025
c4b755b
updating the desctiption and references
umfranci Feb 12, 2025
7c23f86
Updating variable name and noqa
umfranci Feb 12, 2025
38d1214
Removing trailing spaces
umfranci Feb 13, 2025
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24 changes: 11 additions & 13 deletions microsoft/testsuites/core/lsvmbus.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@
from lisa.operating_system import BSD, Windows
from lisa.sut_orchestrator import AZURE
from lisa.sut_orchestrator.azure.tools import VmGeneration
from lisa.tools import Cat, Ls, Lscpu, Lsvmbus
from lisa.tools import Cat, Ethtool, Ls, Lscpu, Lsvmbus
from lisa.tools.lsvmbus import VmBusDevice
from lisa.util import LisaException
from lisa.util.perf_timer import create_timer
Expand Down Expand Up @@ -105,13 +105,9 @@ def verify_vmbus_devices_channels_bsd(self, node: Node) -> None:
- Synthetic keyboard
2. Check that each netvsc and storvsc SCSI device have correct number of vmbus
channels created and associated.
2.1 Check expected channel count of each netvsc is min (num of vcpu, 8).
2.1.1 Caculate channel count of each netvsc device.
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/net/hyperv/rndis_filter.c#n1548 # noqa: E501
2.2.2 Cap of channel count of each netvsc device.
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/net/hyperv/hyperv_net.h#n877 noqa: E501
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/net/hyperv/rndis_filter.c#n1551 noqa: E501

2.1 Check expected channel count of each netvsc matches that obtained from the ethtool.
2.1.1 Get expected channel count of netvsc from ethtool.
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/net/hyperv/netvsc_drv.c#n2001 # noqa: E501
2.2 Check expected channel count of each storvsc SCSI device is min (num of
vcpu/4, 64).
2.2.1 Caculate channel count of each storvsc SCSI device.
Expand All @@ -134,11 +130,13 @@ def verify_vmbus_devices_channels(self, node: Node) -> None:
# vmbus channels created and associated.
lscpu_tool = node.tools[Lscpu]
core_count = lscpu_tool.get_core_count()
# Each netvsc device should have "the_number_of_vCPUs" channel(s)
# with a cap value of 8.
expected_network_channel_count = min(core_count, 8)
# Each storvsc SCSI device should have "the_number_of_vCPUs / 4" channel(s)
# with a cap value of 64.

# 2.1 Get expected channel count of each netvsc is min (num of vcpu, 8).
expected_network_channel_count = (
node.tools[Ethtool].get_device_channels_info("eth0", True)
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it is possible that case will change the combined channel count

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I think it is the actual value, not the expected value.

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I think it is the actual value, not the expected value.

Agree, the value should be calculated, instead of getting from the system. This test case is to verify if the count of channel is the same as designed.

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Thanks for the review team. If the logic for channel calculation is updated and the said patch is available only in certain distros - it would cause the test to fail in certain cases and to succeed in others, thus creating a discrepancy. The current patch is available in SLES and Upstream but not in other distros. How can we alter the test cases to handle different logics for different situations?
Also, to avoid such a situation, wouldn't it be helpful to use a tool which refers the relevant channel calculation code at the Kernel level?

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Can it be differentiated by kernel version?

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We can do that for a short-term solution but as the patch is backported, we would need to update the kernel version for the test case.

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We can do that for a short-term solution but as the patch is backported, we would need to update the kernel version for the test case.

If the patch is backported, all newer version can use the new algorithm. So, the test cases can work with both old and newer versions.

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Thanks for the inputs @squirrelsc . Started an internal thread on this to get inputs from the Kernel team as well.

).current_channels

# 2.2 Get expected channel count of each storvsc SCSI device
if node.nics.is_mana_device_present():
expected_scsi_channel_count = min(core_count, 64)
else:
Expand Down
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