Re: Linux 5.11-rc5

[Mike Rapoport]

On Mon, Jan 25, 2021 at 12:49:39PM -0800, Linus Torvalds wrote:
> On Mon, Jan 25, 2021 at 12:35 PM Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
> 
> Mike: should we perhaps revert the first patch too (commit
> bde9cfa3afe4: "x86/setup: don't remove E820_TYPE_RAM for pfn 0")?

Unfortunately, I was too optimistic and didn't take into account that this
commit changes the way /dev/mem sees the first page of memory.

There were reports of slackware users about issues with lilo after upgrade
from 5.10.11 to 5.10.12

https://www.linuxquestions.org/questions/slackware-14/slackware-current-lilo-vesa-warnings-after-recent-updates-4175689617/#post6214439 

The root cause is that lilo is no longer able to access the first memory
page via /dev/mem because its type was changed from E820_TYPE_RESERVED to
E820_TYPE_RAM, so this became a part of the "System RAM" resource and
devmem_is_allowed() considers it disallowed area.

So here's the revert of bde9cfa3afe4 as well.