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On Aarch64 systems we do not normalize vCPUs, we let KVM configure them. This means that the CPU cache hierarchy exposed to the guest depends entirely on what the KVM decides it to be.

We observed that when we're running tests on Ubuntu hosts with a 6.14 kernel the cache hierarchy is different than the one we expect on AL hosts.

Until we decide how to deal with CPU hierarchy in a controlled way (or not) skip the test on Ubuntu systems.

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@bchalios bchalios added the Status: Awaiting review Indicates that a pull request is ready to be reviewed label Oct 30, 2025
@bchalios bchalios enabled auto-merge (rebase) October 30, 2025 12:32
kalyazin
kalyazin previously approved these changes Oct 30, 2025
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codecov bot commented Oct 30, 2025

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.84%. Comparing base (d33011c) to head (3211563).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files
@@           Coverage Diff           @@
##             main    #5496   +/-   ##
=======================================
  Coverage   82.84%   82.84%           
=======================================
  Files         269      269           
  Lines       27737    27737           
=======================================
  Hits        22978    22978           
  Misses       4759     4759           
Flag Coverage Δ
5.10-m5n.metal 83.01% <ø> (ø)
5.10-m6a.metal 82.28% <ø> (+<0.01%) ⬆️
5.10-m6g.metal 79.66% <ø> (-0.01%) ⬇️
5.10-m6i.metal 83.01% <ø> (ø)
5.10-m7a.metal-48xl 82.27% <ø> (ø)
5.10-m7g.metal 79.66% <ø> (-0.01%) ⬇️
5.10-m7i.metal-24xl 82.98% <ø> (ø)
5.10-m7i.metal-48xl 82.98% <ø> (-0.01%) ⬇️
5.10-m8g.metal-24xl 79.66% <ø> (ø)
5.10-m8g.metal-48xl 79.66% <ø> (ø)
6.1-m5n.metal 83.04% <ø> (ø)
6.1-m6a.metal 82.31% <ø> (ø)
6.1-m6g.metal 79.66% <ø> (-0.01%) ⬇️
6.1-m6i.metal 83.03% <ø> (-0.01%) ⬇️
6.1-m7a.metal-48xl 82.30% <ø> (ø)
6.1-m7g.metal 79.66% <ø> (-0.01%) ⬇️
6.1-m7i.metal-24xl 83.05% <ø> (-0.01%) ⬇️
6.1-m7i.metal-48xl 83.05% <ø> (+<0.01%) ⬆️
6.1-m8g.metal-24xl 79.66% <ø> (ø)
6.1-m8g.metal-48xl 79.66% <ø> (ø)

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@bchalios bchalios force-pushed the skip_cpu_topology_test_on_ubuntu branch 3 times, most recently from a6ebc9a to 9cbf236 Compare October 30, 2025 15:33
On Aarch64 systems we do not normalize vCPUs, we let KVM configure them.
This means that the CPU cache hierarchy exposed to the guest depends
entirely on what the KVM decides it to be.

We observed that when we're running tests on Ubuntu hosts with a 6.14
kernel the cache hierarchy is different than the one we expect on AL
hosts.

Until we decide how to deal with CPU hierarchy in a controled way (or
not) skip the test on Ubuntu systems. The actual test checks that the
host kernel version is greater or equal to 6.14.

Signed-off-by: Babis Chalios <[email protected]>
@bchalios bchalios force-pushed the skip_cpu_topology_test_on_ubuntu branch from 9cbf236 to 3211563 Compare October 30, 2025 15:36
@bchalios bchalios merged commit f5c2674 into firecracker-microvm:main Oct 30, 2025
7 checks passed
@bchalios bchalios deleted the skip_cpu_topology_test_on_ubuntu branch October 30, 2025 17:22
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