[LAU] reducing xruns (System configuration)

[Ralf Mardorf]

On Fri, 20 Jul 2018 22:02:05 -1000, david wrote:
>On 07/19/2018 11:56 PM, Ralf Mardorf wrote:
>> 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.

At the moment I test 'nopti' again for a non-audio session.

[rocketmouse at 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 21 02:34 meltdown
-r--r--r-- 1 root root 4.0K Jul 21 02:34 spec_store_bypass
-r--r--r-- 1 root root 4.0K Jul 21 02:34 spectre_v1
-r--r--r-- 1 root root 4.0K Jul 21 02:34 spectre_v2
Vulnerable
Vulnerable
Mitigation: __user pointer sanitization
Mitigation: Full generic retpoline, IBPB, IBRS_FW

It doesn't solve some issues on my machine and at least for non-audio a
possible better performance of my computer isn't of value to disable
PTI.

I'll build 4.16.18-rt10 now, maybe it takes less time than I needed to
build 4.16.18-rt9 with PTI enabled.