Kitz Forum
Computers & Hardware => PC Hardware => Topic started by: broadstairs on August 17, 2018, 08:40:33 AM
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A new issue has arisen with Intel processors, not present in AMD though. See https://www.theregister.co.uk/2018/08/14/intel_l1_terminal_fault_bugs/ (https://www.theregister.co.uk/2018/08/14/intel_l1_terminal_fault_bugs/) here for one description. This could be as bad as Meltdown etc.....
Stuart
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Do you think we can expect another drop in performance after they fix this? That would suck.
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Not much detail in the stuff I read but I suspect that they have been able to improve things without crucifying performance. Disabling hyper threading in one case will knock out what 5-15% performance in some cases but I do not like hyper threading much as I suspect there are even cases where unfortunate software can end up going slower with hyper threading on than off and it is better to turn it off.
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Linux 4.18.1, my cpu bug list is getting quite long:
$ cat /proc/cpuinfo
model name : Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz
bugs : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf
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Here's a simple shell script that might be useful --
#!/bin/sh
/bin/echo -e "Kernel -- \c"
/bin/uname -r
if [ -d /sys/devices/system/cpu/vulnerabilities ]; then
if [ -r /sys/devices/system/cpu/vulnerabilities/l1tf ]; then
/bin/echo -e "L1tf -- \c"
/bin/cat /sys/devices/system/cpu/vulnerabilities/l1tf
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/meltdown ]; then
/bin/echo -e "Meltdown -- \c"
/bin/cat /sys/devices/system/cpu/vulnerabilities/meltdown
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/spec_store_bypass ]; then
/bin/echo -e "Speculative Store Bypass -- \c"
/bin/cat /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/spectre_v1 ]; then
/bin/echo -e "Spectre v1 -- \c"
/bin/cat /sys/devices/system/cpu/vulnerabilities/spectre_v1
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/spectre_v2 ]; then
/bin/echo -e "Spectre v2 -- \c"
/bin/cat /sys/devices/system/cpu/vulnerabilities/spectre_v2
fi
else
/bin/echo " -- No data available."
fi
exit 0
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They do need to start and think what they are doing, need a department if black hats against the design teams doing the evil before the processors get released.
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Here's a simple shell script that might be useful --
Nice one:
eric@great-tit:~$ ./vulnerability-check
Kernel -- 4.9.0-7-amd64
Meltdown -- Mitigation: PTI
Speculative Store Bypass -- Vulnerable
Spectre v1 -- Mitigation: __user pointer sanitization
Spectre v2 -- Mitigation: Full generic retpoline, IBPB, IBRS_FW
eric@great-tit:~$
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Having recently become aware of the latest vulnerability, SRBDS, I thought it was time to update the shell-script.
#!/bin/bash
echo -e "Kernel -- \c"
uname -r
if [ -d /sys/devices/system/cpu/vulnerabilities ]; then
if [ -r /sys/devices/system/cpu/vulnerabilities/itlb_multihit ]; then
echo -e "Itlb Multihit -- \c"
cat /sys/devices/system/cpu/vulnerabilities/itlb_multihit
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/l1tf ]; then
echo -e "L1TF -- \c"
cat /sys/devices/system/cpu/vulnerabilities/l1tf
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/mds ]; then
echo -e "MDS -- \c"
cat /sys/devices/system/cpu/vulnerabilities/mds
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/meltdown ]; then
echo -e "Meltdown -- \c"
cat /sys/devices/system/cpu/vulnerabilities/meltdown
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/spec_store_bypass ]; then
echo -e "Speculative Store Bypass -- \c"
cat /sys/devices/system/cpu/vulnerabilities/spec_store_bypass
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/spectre_v1 ]; then
echo -e "Spectre v1 -- \c"
cat /sys/devices/system/cpu/vulnerabilities/spectre_v1
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/spectre_v2 ]; then
echo -e "Spectre v2 -- \c"
cat /sys/devices/system/cpu/vulnerabilities/spectre_v2
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/srbds ]; then
echo -e "Srbds -- \c"
cat /sys/devices/system/cpu/vulnerabilities/srbds
fi
if [ -r /sys/devices/system/cpu/vulnerabilities/tsx_async_abort ]; then
echo -e "TSX Async Abort -- \c"
cat /sys/devices/system/cpu/vulnerabilities/tsx_async_abort
fi
else
echo " -- No data available."
fi
exit 0
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Not much detail in the stuff I read but I suspect that they have been able to improve things without crucifying performance. Disabling hyper threading in one case will knock out what 5-15% performance in some cases but I do not like hyper threading much as I suspect there are even cases where unfortunate software can end up going slower with hyper threading on than off and it is better to turn it off.
That's a very random theory you have there, can't say I've seen a shred of evidence to back that up on current software.
I mean sure, maybe a decade or so ago that was true, but today hyperthreading make a big difference.