Re: [TECH TOPIC] Reaching consensus on CONFIG_HIGHMEM phaseout
From: Matthew Wilcox <willy@infradead.org>
Date: 2025-09-10 14:04:59
Also in:
imx, linux-arm-kernel, linux-mips, linux-mm, lkml
On Wed, Sep 10, 2025 at 03:10:05PM +0200, Linus Walleij wrote:
This is is done so that we can unmap *most* of the kernel memory but *keep* the VMALLOC area, so that e.g. exceptions can still execute and save to stack when they occur, and we can call into the kernel to execute said exceptions. This in practice means the area 0xf1000000-0xffffffff which also includes the high exception vectors that must for natural reasons also be kept in the mapping. What we have mapped today (all of the time) is 0xc0000000-0xffffffff. A minimal 256 MB mapping from 0xf0000000-0xffffffff should be able to cover this.
Can I ask where the MMIO (PCI?) window lives?