l1tf: Kernel suggests I throw away third of my memory. I'd rather not
From: Pavel Machek
Date: Wed Oct 17 2018 - 06:56:15 EST
6a012288 suggests I throw away 1GB on RAM. On 3GB system.. that is not
going to be pleasant.
# The Linux kernel contains a mitigation for this attack vector, PTE
# inversion, which is permanently enabled and has no performance
I don't believe it has "no" performance impact, but I guess it is lost
in the noise.
# The kernel ensures that the address bits of PTEs, which are
# not marked present, never point to cacheable physical memory space.
# A system with an up to date kernel is protected against attacks from
# malicious user space applications.
These are not true.
Linux amd 4.19.0-rc8-next-20181017autobisect1539371050 #189 SMP Wed
Oct 17 12:04:23 CEST 2018 i686 GNU/Linux
Now question is... can we do better? Kernel stores information about
swapped-out pages there, right? That sounds like a cool hack, but
maybe it is time to get rid of that hack?
As a workaround, can I simply do swapoff -a to be safe for now?
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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