Louwrentius

Context

I'm running a virtualisation lab environment, with four Intel-based CPUs (i5-6500) and one AMD Ryzen 3 PRO 2200GE.

When migrating virtual machines from one of the Intel hosts to the AMD host, the migration would fail with the following error:

error: operation failed: guest CPU doesn't match specification: extra features: cmp_legacy"

The really strange thing is that some virtual machines did migrate successfully from an Intel system to the AMD system without any issues.

So I dumped the XML of the virtual machines and compared them. It turns out that the virtual machines that migrated successfully were all single-core and all failing virtual machines were multi-core.

As the cmp_legacy CPU feature seems to be related to (lack of) support for hyper-threading, the configured CPU topology of the virtual machines was suspected to be the culprit.

I've configured a custom CPU topology on the virtual machines with 1 socket, 1 die and one or more CPU cores. This caused the migration failure.

Solution

If you configure multi-core virtual machines with multiple sockets instead of cores migration between Intel and AMD hosts will succeed.

In the past, migrations between an Intel and AMD host always succeeded, assuming that the appropriate CPU features were disabled. Why this suddenly stopped working is not clear to me, as this configuration never changed. Maybe it's related to a Libvirt update, but I have no proof for this.

Skip to the bottom two paragraph for instructions on how to replace the battery.

I bought my Bose SoundLink on-ear Bluetooth headphones for 250 Euros around 2017 and I really like them. They are small, light, comfortable and can easily fit in a coat pocket when folded.

Up until now (about 7 years later) I have replaced the ear cushions in 2019 (€25) and 2024 (€18).

Early 2025, battery capacity had deteriorated to a point where it became noticeable. The battery was clearly dying.

Unfortunately these headphones aren't designed for easy battery replacement:

• Bose hasn't published instructions on how to replace the battery, doesn't offer a replacement battery and hasn't documented which battery type/model is used.
• The left 'head phone' has two Torx security screws and most people won't have the appropriate screwdriver for this size
• There is soldering involved

I wanted to try a battery replacement anyway as I hate to throw away a perfectly good, working product just because the battery has worn out. Maybe at some point the headband needs replacing, but with a fresh battery, these headphones can last another 7 years. Let's prevent a bit of e-waste with a little bit of cost and effort.

Most of all, the cost of this battery replacement is much lower than a new pair of headphones as the battery was €18 including taxes and shipping.

Right to repair should include easy battery replacement

Although my repair seemed to have worked out fine, it requires enough effort that most people won't even try. For this reason, I feel that it should be mandatory by law that:

1. Batteries in any product must be user-replaceable (no special equipment or soldering required)
2. Batteries must be provided by the vendor until 10 years after the last day the product was sold (unless it's a standard format like AA(A) or 18650).
3. Batteries must be provided at max 10% of the cost of the original product
4. The penalty for non-compliance should be high enough such that it won't be regarded as the cost of doing business

For that matter, all components that may wear down over time should be user-replaceable.

What you need to replace the battery

1. Buy the exact battery type: ahb571935pct-01 (350mAh) (notice the three wires!)
2. A Philips #0 screwdriver / bit
3. A Torx T6H security screwdriver / bit (iFixit kits have them)
4. A soldering iron
5. Solder
6. Heat shrink for 'very thin wire'
7. Multimeter (optional)
8. a bit of tape to 'cap off' bare battery leads

Please note that I found another battery ahb571935pct-03 with similar specifications (capacity and voltage) but I don't know if it will fit.

Putting the headphone ear cushion back on can actually be the hardest part of the process, you need to be firm and this process is documented by Bose.

Battery replacement steps I took

Make sure you don't short the wires on the old or new battery during replacement

The battery is located in the left 'head phone'.

1. Use a multimeter to check if your new battery isn't dead (should be 3+ volt)
2. Remove the ear cushion from the left 'head phone' very gently as not to tear the rim
3. Remove the two philips screws that keep the driver (speaker) in place
4. Remove the two Torx screws (you may have to press a bit harder)
5. Remove the speaker and be carefull not to snap the wire
6. Gently remove the battery from the 'head phone'
7. Cut the wires close to the old battery (one by one!) and cover the wires on the battery to prevent a short
8. Strip the three wires from the headphones a tiny bit (just a few mm)
9. Put a short piece of heat shrink on each of the three wires of the battery
10. Solder each wire to the correct wire in the ear cup
11. Adjust the location of the heat shrink over the freshly soldered joint.
12. Use the soldering iron close to the heat shrink to shrink it (don't touch anything), this can take some time, be patient
13. Check that the heat shrink is fixed in place and can't move
14. Put the battery into it's specific location in the back of the 'head phone'
15. Test the headphones briefly before reassembling the headphones
16. Reassemble the 'head phone' (consider leaving out the two Torx screws)
17. Dispose of the old battery in a responsible manner