RE: [PATCH v2 1/6] x86/bugs: Add asm helpers for executing VERW

[Luck, Tony]

> Sure it could, but it would mean the kernel is sitting on an average of 6 MB of unusable memory. It would also mean that unloaded modules would create holes in that memory which would have to be managed.

On my Fedora38 desktop:

$ lsmod | awk '{ bytes += $2 } END {print bytes/(1024*1024)}'
21.0859

Lots more than 6MB memory already essentially pinned by loaded modules.

$ head -3 /proc/meminfo
MemTotal:       65507344 kB
MemFree:        56762336 kB
MemAvailable:   63358552 kB

Pinning 20 or so Mbytes isn't going to make a dent in that free memory.

Managing the holes for unloading/reloading modules adds some complexity ... but shouldn't be awful.

If this code managed at finer granularity than "page", it would save some memory.

$ lsmod | wc -l
123

All those modules rounding text/data up to 4K boundaries is wasting a bunch of it.

-Tony