REBAR production makes hot plugging unworkable for monitoring systems
REBAR production makes hot plugging unworkable for monitoring systems
Hello, I recently needed to replace my motherboard because the previous one failed. I installed an MSI PRO B550m vc WI-FI. My Radeon RX 7600 is a Lenovo OEM card and paired with a Ryzen 5 5600. I'm running Fedora KDE 42. I don't recall if ReBAR was turned on or if it was enabled by default—it stayed on until today. For the past few weeks, the system has run smoothly, but this week, while working with one monitor and a Raspberry Pi, I disabled the display software for the Pi so it wouldn’t take over when the device restarted. That worked initially, but after finishing with the Pi, I re-enabled it and the computer froze. I had to power cycle it manually.
I tried everything else—Windows 10, Kubuntu, even physically unplugging the display—but all resulted in freezing. In Kubuntu, enabling or connecting a second display caused the system to lock up, and after rebooting it retained the previous settings, leaving only one display active. The login screen appeared on both displays in Kubuntu, but when the desktop loaded, the disabled one would turn off.
I went into the BIOS and adjusted PCIe settings like SR-IOV and data link features, but nothing changed until I turned ReBAR off. Disabling ReBAR resolved the problem. Now I can enable/disable displays across all OSes without issues, and I can plug in/remove any monitor without trouble. Still wondering if having ReBAR enabled is preventing hot-plugging monitors. Have others faced similar problems? Is there an issue with my graphics card or motherboard? Thanks!
It looks quite unusual. It might be related to a kernel problem or a specific UI like GNOME.
At first I assumed this, so I tried Windows 10 and a Linux distro called Kubuntu. The results were consistent across all three systems, and everything seemed to work better once ReBAR was turned off. Quite strange!
Absolutely! Here’s a rephrased version of your message:
Yeah, I didn’t realize that. The screen I turned off for the Pi actually has both HDMI and DisplayPort ports. It connects to my PC via the DP port, and I always use an HDMI cable for Pi tasks or anything needing a display. The other screen is only linked through HDMI, and I’ve tried all the possible settings—disabling the display, unplugging it, testing different operating systems. Everything was fresh at the time of setup: I did a complete reinstall after replacing the motherboard and updated the BIOS right away. I reached out to the support team for advice, and they recommended checking the VBIOS settings, thinking it might be a firmware problem. However, I can’t find any way to update VBIOS, and since it’s an OEM graphics card, I’m not sure Lenovo releases updates for it.
I also wondered if enabling ReBAR on the old motherboard would have made a difference, but I haven’t looked into that. It’s strange—my PC still works fine even with ReBAR off, so I’m confused about what it does. I didn’t bother investigating further because I wasn’t sure its purpose or how it might affect my setup.
It seems like the issue only appeared when ReBAR was disabled, which is confusing. Thanks for sharing this!