OVMF or SeaBios what is best and why?


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Performance wise, there should be no difference, other than people with specific issues that are fixed by using UEFI/OVMF.

SeaBIOS is apparently quite the hackery for VGA arbitration, and (as you may be aware) breaks the console output once you start a VM using it.

Here's a quote from Alex Williamson of Redhat/VFIO

""The VGA space itself is a shared resource, so every time the guest tries to access VGA space it gets gets trapped into QEMU, which forwards the request to VFIO, which negotiates with the VGA arbiter and adjusts chipset routing as necessary.  Therefore VGA mode is bearable when there's one consumer, once you start getting contention and the arbiter needs to switch routing on each access, this can certainly become a bottleneck.  However, even when using a legacy BIOS with x-vga, those VGA accesses *only* occur during early boot or if you're using non-accelerated drivers, so the window for contention is very small.  Once the guest is up and running, access to legacy VGA space ceases, and there's no performance difference between legacy BIOS and UEFI that I'm aware of."

https://www.redhat.com/archives/vfio-users/2016-February/msg00036.html

So UEFI is certainly the "way forward" and allows you to initiate a GPU after the initial POST, etc.

 

My recommendation is this:

If you're setting up a new VM, choose OVMF/UEFI. We initially had the issue of not being able to have more than 1 OVMF VM, so I stuck with SeaBIOS, but that is fixed now.

 

If you already have working VM's (I have 4 this way) and the downside of this doesn't bother you (losing console, maybe also the new GUI boot mode), leave them alone and continue to use as is.

There is a way to switch a Windows VM to UEFI, but it doesn't look to be very straight forward (from what I've read), and is likely easier to just reinstall.

 

 

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