Module pat 

Page Attribute Table (PAT) initialization for write-combining memory.

Reprograms PAT entry 1 from WT (write-through) to WC (write-combining), then provides apply_write_combining() to set framebuffer page table entries to use the WC memory type. This yields 5-150x faster MMIO writes for the fbcon flush path.

PAT index mapping after init()

Index	PWT	PCD	PAT	Type
0	0	0	0	WB
1	1	0	0	WC (was WT)
2	0	1	0	UC-
3	1	1	0	UC
4-7			1	(mirrors 0-3 by default)

Framebuffer PTEs use index 1 (PWT=1, PCD=0, PAT=0) for write-combining.

Functions

apply_write_combining^⚠

Apply write-combining attributes to a virtual address range.

init

Reprogram PAT entry 1 from WT to WC.