[vfio-users] [FEEDBACK NEEDED] Additionnal tips to include in the Arch wiki article

Nicolas Roy-Renaud nicolas.roy-renaud.1 at ens.etsmtl.ca
Sun May 22 14:56:48 UTC 2016


I remember trying that before I ended up switching my guest GPU to 
secondary, and I'd get the exact same symptoms (no input on the guest 
monitor, everything still boots normally) except without any kind of 
error message this time around. Are you recommanding to simply avoid 
booting off the boot VGA device altogether?


On 2016-05-20 16:27, Alex Williamson wrote:
>
> The boot VGA ROM is handled differently from other PCI ROMs in Linux, 
> when you read it you're actually reading a shadow copy of it placed at 
> 0xc0000, which has its roots back in the original IBM PC history.  
> Execution of the VGA ROM is allowed to modify this copy of the ROM 
> image in memory.  Thus you're really not getting a pristine copy of 
> the device ROM and it can often lead to these invalid ROM contents 
> messages.  I wish we provided raw access to the PCI option ROM in 
> these cases as well.  For now, if you do have these sorts of invalid 
> ROM messages, I would suggest that you at least boot with the card as 
> secondary, dump the ROM, then use that collected image with the 
> romfile= option rather than use the shadow copy.  I had to add some 
> code to vfio to fix device IDs and checksums for IGD assignment 
> because of this, I don't know if there's any standard fixup we can do 
> for other vendors.  Thanks,




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