Hello, I also checked for what Chris said what you wish to do not being supported and he is correct, sorry we can't be of help further.
Dear, I have a T640 tower, and the BIOS is upgraded to 2.16.1 Is above 4g same as resizable bar? or how to enable resizable bar? BIOS setting: UEFI mode Above 4g is enabled (by default) MMIO base is 56T OS Ubuntu 22.04 Logs: [ 8.166136] i915 0000:db:00.0: BAR 0: releasing [mem 0xef000000-0xefffffff 64bit][ 8.166139] i915 0000:db:00.0: BAR 2: releasing [mem 0x39ffe0000000-0x39ffefffffff 64bit pref][ 8.166176] i915 0000:db:00.0: BAR 2: no space for [mem size 0x400000000 64bit pref][ 8.166178] i915 0000:db:00.0: BAR 2: failed to assign [mem size 0x400000000 64bit pref][ 8.166180] i915 0000:db:00.0: BAR 0: assigned [mem 0xef000000-0xefffffff 64bit][ 8.166277] i915 0000:db:00.0: [drm] Failed to resize BAR2 to 16384M (-ENOSPC)[ 8.166280] i915 0000:db:00.0: BAR 2: assigned [mem 0x39ffe0000000-0x39ffefffffff 64bit pref][ 8.166318] i915 0000:db:00.0: [drm] Local memory IO size: 0x0000000010000000[ 8.166319] i915 0000:db:00.0: [drm] Local memory available: 0x00000002fb000000[ 8.166321] i915 0000:db:00.0: [drm] Using a reduced BAR size of 256MiB. Consider enabling 'Resizable BAR' or similar, if available in the BIOS.  
T640 resizable bar is available or not?