It looks like you’re 1 generation early on that 8930.
You could pull the 8940 bios and see if it’s possible/how it’s done. But that board is different than the board they were using from 8910-8930.
What makes modding Dells so difficult is, I think, a lack of direct Padding area under drivers, and related FPT protected regions. It may not be impossible, but it sure wouldn’t be easy, and it may require a programmer after hex editor work. I think you’re making the right call in leaving it be.
Late Edit 1: After looking at Kuri0’s Resizable BAR BIOS EFI Module topic, and then her github page, and then downloading the latest XPS 8930 bios upgrade from Dell and examining it with UEFITool NE, as far as enabling resizable bar is concerned:
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A Header only GUID search for
3C1DE39F-D207-408A-AACC-731CFB7F1DD7
brings up a cyan colored Volume and sub-Volume. I believe they’re protected. -
Kuri0’s ReBarDxe.ffs is too big to fit into (or at the bottom of) the Volume GUID: 5C60F367-A505-419A-859E-2A4FF6CA6FE5. Direct underlying (and cyan colored) Volume free space is too small.
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PCIe Resizable Base Address Register (BAR) is not a present, but hidden feature in the XPS 8930 bios. It would have to be added. That bios region is protected and the direct sub-Volume free space is too small to make adding the feature reasonably possible.
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However, running this through UEFI-Editor, I am seeing that Above 4GB MMIO BIOS assignment is enabled, for what that’s worth.