On 07/19/2018 11:56 PM, Ralf Mardorf wrote:
On Fri, 20 Jul 2018 11:24:57 +0200, David Kastrup wrote:
So the idea to take this into low-latency realms with a view on
realtime effects seems a bit optimistic indeed.
;)
On Thu, 19 Jul 2018 22:52:45 -1000, _another_ david wrote:
I first tried it with 4.13.x and decided that items like random
kernel panios, system freezes and crashes weren't very good ways to
defend against Spectre/Meltdown/DOS. ;)
Actually freezes and crashes do defend against attacks :D. But you are
right, for Claws and Firefox I'm experiencing way to often serious
issues and for virtualbox at least way to often an annoyance for an
unexplained reason.
I at least should test using it with PTI disabled.
The current default on my machine is:
[rocketmouse@archlinux ~]$ ls -hAl /sys/devices/system/cpu/vulnerabilities/; cat /sys/devices/system/cpu/vulnerabilities/*
total 0
-r--r--r-- 1 root root 4.0K Jul 20 10:12 meltdown
-r--r--r-- 1 root root 4.0K Jul 20 10:12 spec_store_bypass
-r--r--r-- 1 root root 4.0K Jul 20 10:12 spectre_v1
-r--r--r-- 1 root root 4.0K Jul 20 10:12 spectre_v2
Mitigation: PTI
Vulnerable
Mitigation: __user pointer sanitization
Mitigation: Full generic retpoline, IBPB, IBRS_FW
'nopti' only would disable PTI, but keep the spectre mitigations. While
PTI is part of the kernel, the spectre mitigations are likely part
of the µcode. However, if I would run my CPU without the µcode, I
perhaps would get rid of the spectre mitigation, but IIRC I
unfortunately would get rid of TSC, too.
The Spectre mitigations don't seem to affect the performance on my
desktop, which is running with PTI off but with the mitigation microcode
patches. I also have Spectre mitigations on my Intel laptop with no
performance impact.
--
David W. Jones
gnome@xxxxxxxxxxxxx
authenticity, honesty, community
http://dancingtreefrog.com
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