Increase PCIe port limit in workshop VMs

[jonathan-conder]

Description

Increases the default PCIe port limit for workshops with several SDKs. This is needed to accomodate the SDK mounts themselves, and any connected mount plugs.

With a lot of SDKs (i.e. a lot of PCIe ports), LXD's patched OVMF firmware likes to reboot the instance to reallocate enough memory for them in a contiguous block. We probably should have already supported mid-boot reboots since it's not as uncommon as you might think, e.g.: https://github.com/canonical/lxd/blob/85f897013ccdb0f8f44d434a3b655d2edcefcfae/lxd-agent/main_agent.go#L98-L113

Unfortunately LXD doesn't tell us if the instance is rebooting or just powering down; in any case we probably shouldn't wait for it to reboot indefinitely. 10s seems to be enough time, in a nested VM it only takes about 3s to go from no QEMU to "QEMU running," we don't need to wait for systemd or anything.

Self-review quick check

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• I confirm the PR has no implications for documentation.

[Copilot]

🟡 Changes recommended

The VM snapshot fixture will fail, and the reboot test does not verify that startup survives a completed reboot.

2 open findings

• Update VM snapshot fixture for new limits and removed i8042 · New
• Verify actual reboot before asserting workshop restart completion · New

What changed in this PR

This PR raises PCIe port and CPU limits for LXD virtual-machine workshops with many SDK mounts and allows startup to wait through an initial reboot.

Changes:

• Scale VM port and CPU limits with the number of SDKs.
• Add reboot and limit tests.
• Document VM connection limits and add PCIe to the documentation wordlist.

File	Description
internal/​workshop/​lxd/​tests/​integration/​workshop_test.go	Adds reboot and default-port integration tests.
internal/​workshop/​lxd/​lxd_backend.go	Sets VM limits and waits for startup after a reboot.
internal/​workshop/​lxd/​lxd_backend_test.go	Tests VM limit calculations.
docs/​reference/​workshops.rst	Describes VM port and processor limits.
docs/​how-to/​customize-workshops/​use-virtual-machines.rst	Explains virtual-hardware constraints.
docs/​.custom_wordlist.txt	Adds “PCIe” to the wordlist.

🧠 Review effort: Lite

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