Original Thread

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TLDR;

Copying from the thread on 4chan

There is evidence of a massive Intel CPU hardware bug (currently under embargo) that directly affects big cloud providers like Amazon and Google. The fix will introduce notable performance penalties on Intel machines (30-35%).

People have noticed a recent development in the Linux kernel: a rather massive, important redesign (page table isolation) is being introduced very fast for kernel standards... and being backported! The "official" reason is to incorporate a mitigation called KASLR... which most security experts consider almost useless. There's also some unusual, suspicious stuff going on: the documentation is missing, some of the comments are redacted (https://twitter.com/grsecurity/status/947147105684123649) and people with Intel, Amazon and Google emails are CC'd.

According to one of the people working on it, PTI is only needed for Intel CPUs, AMD is not affected by whatever it protects against (https://lkml.org/lkml/2017/12/27/2). PTI affects a core low-level feature (virtual memory) and has severe performance penalties: 29% for an i7-6700 and 34% for an i7-3770S, according to Brad Spengler from grsecurity. PTI is simply not active for AMD CPUs. The kernel flag is named X86_BUG_CPU_INSECURE and its description is "CPU is insecure and needs kernel page table isolation".

Microsoft has been silently working on a similar feature since November: https://twitter.com/aionescu/status/930412525111296000

People are speculating on a possible massive Intel CPU hardware bug that directly opens up serious vulnerabilities on big cloud providers which offer shared hosting (several VMs on a single host), for example by letting a VM read from or write to another one.

EDIT1: the examples of the i7 series, are just examples. This affects all Intel platforms as far as I can tell.

EDIT2: Thank you for the gold /u/tipsle!

EDIT3: Thanks to Aiber for the synthetic test on Linux with the latest patches. Doing tasks that require a lot of syscalls will see the most performance hit. Compiling, virtualization, etc. Whether day to day usage, gaming, etc will be affected remains to be seen. But as you can see below, up to 4x slower speeds with the patches...

This was tested on an i6700k, just so you have a feel for the processor this was performed on.

#include <unistd.h>
#include <sys/syscall.h>
#include <stdio.h>


// gcc -Wall -O3 -o getpid getpid.c

/*
[    0.000000] Linux version 4.15.0-rc6-mainline (user@machine) (gcc version 7.2.1 20171128 (GCC)) #1 SMP PREEMPT Tue Jan 2 09:30:19 UTC 2018

[user@machine getpid]$ time ./getpid
1069

real    0m15.351s
user    0m6.900s
sys     0m8.447s
[user@machine getpid]$ time ./getpid
1130

real    0m15.349s
user    0m6.910s
sys     0m8.437s
[user@machine getpid]$ time ./getpid
1174

real    0m15.393s
user    0m7.022s
sys     0m8.365s
[user@machine getpid]$ time ./getpid
1211

real    0m15.424s
user    0m7.037s
sys     0m8.381s

*/

/*
[    0.000000] Linux version 4.14.8-1-ARCH (user@machine) (gcc version 7.2.1 20171128 (GCC)) #1 SMP PREEMPT Wed Dec 20 21:27:44 UTC 2017

[user@machine getpid]$ time ./getpid
1108

real    0m3.814s
user    0m1.266s
sys     0m2.525s
[user@machine getpid]$ time ./getpid
1123

real    0m3.814s
user    0m1.207s
sys     0m2.598s
[user@machine getpid]$ time ./getpid
1131

real    0m3.758s
user    0m1.178s
sys     0m2.579s
[user@machine getpid]$ time ./getpid
1146

real    0m3.790s
user    0m1.270s
sys     0m2.513s
*/

int main(void)
{
    long value;

    for (int i = 0; i < 100000000; i++)
        value = syscall(SYS_getpid);

    printf("%d\n", (int) value);


    return 0;
}

EDIT4: Adding another test from Aiber using iperf. There are some differences, but not hugely significant:

Server: iperf -s -l 1M

Client:

[    0.000000] Linux version 4.15.0-rc6-mainline (user@machine) (gcc version 7.2.1 20171128 (GCC)) #1 SMP PREEMPT Tue Jan 2 09:30:19 UTC 2018

iperf -c localhost -t 30 -i 10 -l 128K
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 2.50 MByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 53432 connected with 127.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  99.6 GBytes  85.6 Gbits/sec
[  3] 10.0-20.0 sec   101 GBytes  86.7 Gbits/sec
[  3] 20.0-30.0 sec   101 GBytes  86.8 Gbits/sec
[  3]  0.0-30.0 sec   302 GBytes  86.3 Gbits/sec

iperf -c localhost -t 30 -i 10 -l 8K
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 2.50 MByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 53434 connected with 127.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  71.0 GBytes  61.0 Gbits/sec
[  3] 10.0-20.0 sec  73.6 GBytes  63.2 Gbits/sec
[  3] 20.0-30.0 sec  73.8 GBytes  63.4 Gbits/sec
[  3]  0.0-30.0 sec   218 GBytes  62.5 Gbits/sec

iperf -c localhost -t 30 -i 10 -l 2K
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 2.50 MByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 53438 connected with 127.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  18.7 GBytes  16.1 Gbits/sec
[  3] 10.0-20.0 sec  18.8 GBytes  16.2 Gbits/sec
[  3]  0.0-30.0 sec  56.3 GBytes  16.1 Gbits/sec

iperf -c localhost -t 30 -i 10 -l 1K
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 2.50 MByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 53440 connected with 127.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  9.38 GBytes  8.06 Gbits/sec
[  3] 10.0-20.0 sec  9.37 GBytes  8.05 Gbits/sec
[  3]  0.0-30.0 sec  28.1 GBytes  8.06 Gbits/sec




[    0.000000] Linux version 4.14.8-1-ARCH (user@machine) (gcc version 7.2.1 20171128 (GCC)) #1 SMP PREEMPT Wed Dec 20 21:27:44 UTC 2017

iperf -c localhost -t 30 -i 10 -l 128K
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 2.50 MByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 50154 connected with 127.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   104 GBytes  89.5 Gbits/sec
[  3] 10.0-20.0 sec   105 GBytes  89.9 Gbits/sec
[  3] 20.0-30.0 sec   103 GBytes  88.4 Gbits/sec
[  3]  0.0-30.0 sec   312 GBytes  89.3 Gbits/sec

iperf -c localhost -t 30 -i 10 -l 8K
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 2.50 MByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 50146 connected with 127.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  74.3 GBytes  63.8 Gbits/sec
[  3] 10.0-20.0 sec  74.7 GBytes  64.2 Gbits/sec
[  3] 20.0-30.0 sec  74.9 GBytes  64.3 Gbits/sec
[  3]  0.0-30.0 sec   224 GBytes  64.1 Gbits/sec

iperf -c localhost -t 30 -i 10 -l 2K
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 2.50 MByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 50148 connected with 127.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  18.7 GBytes  16.1 Gbits/sec
[  3] 10.0-20.0 sec  18.8 GBytes  16.2 Gbits/sec
[  3]  0.0-30.0 sec  56.3 GBytes  16.1 Gbits/sec

iperf -c localhost -t 30 -i 10 -l 1K
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 2.50 MByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 50152 connected with 127.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  9.38 GBytes  8.06 Gbits/sec
[  3] 10.0-20.0 sec  9.38 GBytes  8.06 Gbits/sec
[  3]  0.0-30.0 sec  28.0 GBytes  8.03 Gbits/sec

EDIT5: Phoronix pre/post patch testing underway here.

EDIT6: Gaming doesn't seem to be affected at this time. See here.

EDIT7: AMD patch excludes their processor(s) from this patch here.

EDIT8: Adding this Register article, as it's been linked a few times in the threads.