Re: [WARNING] Intel Skylake/Kaby Lake processors: broken hyper-threading
- Date: Sun, 25 Jun 2017 22:41:55 -0300
- From: Henrique de Moraes Holschuh <hmh@xxxxxxxxxx>
- Subject: Re: [WARNING] Intel Skylake/Kaby Lake processors: broken hyper-threading
Minor update on the issue:
The check command provided in the advisory to test for hyper-threading
doesn't work: it will always report hyper-theading as enabled. A better
command is provided below.
Note: this also means the perl script will give some false-positives.
I apologise for the inconvenience.
On Sun, 25 Jun 2017, Henrique de Moraes Holschuh wrote:
> Once you know your processor model name, you can check the two lists
> * List of Intel processors code-named "Skylake":
> * List of Intel processors code-named "Kaby Lake":
> Some of the processors in these two lists are not affected because they
> lack hyper-threading support. Run the command below in a command line
> shell (e.g. xterm), and it will output a message if hyper-threading is
> grep -q '^flags.*[[:space:]]ht[[:space:]]' /proc/cpuinfo && \
> echo "Hyper-threading is supported"
The above test (using "grep") does not work, and will always report that
hyper-threading is enabled.
Please use the "lscpu" utility from the util-linux package in a command
line shell (e.g. xterm):
If the lscpu output reports: "Thread(s) per core: 2", that means
hyper-threading is enabled and supported.
If the lscpu output reports: "Thread(s) per core: 1", that means
hyper-threading either disabled or not supported. In this case, the
specific defect mentioned in the advisory will not trigger.