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Legacy/CSM + UEFI support in either SeaBIOS or OVFM?


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I'm trying to passthrough a GTX 550 Ti to my Windows 10 VM, which was previously installed using OVFM BIOS, UEFI boot mode, GPT partition. I was using a Radeon HD 6450 passed through.

After attempting to pass through the card unsuccessfully for a few hours, i realized that the new card will not operate properly on a system that does not support Legacy mode (when i put it in my other system to RIP the vBIOS, i had to enable legacy mode before it would boot with that card in at all).

My question is, is there a way to either enable Legacy/CSM mode in OVFM, or else enable UEFI mode in SeaBIOS?

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19 hours ago, CmdrKeen said:

is there a way to either enable Legacy/CSM mode in OVFM, or else enable UEFI mode in SeaBIOS?

No, it's not possible: ovmf boots uefi, seabios boots legacy, that's all; you need to convert your uefi installation to legacy.

I never tried from uefi to legacy, only legacy to uefi, microsoft has an utility for this and it's straight forward.

Try to search in internet, I saw some links pointing to some instructions, so this should be feasible.

Make backups first!

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3 hours ago, ghost82 said:

No, it's not possible: ovmf boots uefi, seabios boots legacy, that's all; you need to convert your uefi installation to legacy.

I never tried from uefi to legacy, only legacy to uefi, microsoft has an utility for this and it's straight forward.

Try to search in internet, I saw some links pointing to some instructions, so this should be feasible.

Make backups first!

Microsoft's utility only goes Legacy -> UEFI, it does not go the other way. 

 

I will need to create a new VM then. Thank you for the info. I will back up my data and start from scratch.

Edited by CmdrKeen
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2 hours ago, CmdrKeen said:

Microsoft's utility only goes Legacy -> UEFI, it does not go the other way.

Yes, correct

2 hours ago, CmdrKeen said:

I will need to create a new VM then

This is not enough, since you have a uefi image and you want it legacy, so first you need to convert the disk or image from uefi to legacy, then you can create the vm.

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1 hour ago, ghost82 said:

This is not enough, since you have a uefi image and you want it legacy, so first you need to convert the disk or image from uefi to legacy, then you can create the vm.

I was going to create a new vdisk for the new VM. I don't tend to re-use vdisks.

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