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When apic=verbose is specified, the LAPIC timer calibration prints its results
to the console. At least while debugging virtualization code, the CPU and bus
frequencies are printed incorrectly.
Specifically, for a 1.7 GHz CPU with 1 GHz bus frequency and HZ=1000,
the log includes a superfluous 0 after the period:
..... calibration result: 999978
..... CPU clock speed is 1696.0783 MHz.
..... host bus clock speed is 999.0978 MHz.
Looking at the code, this only worked as intended for HZ=100. After the fix,
the correct frequency is printed:
..... calibration result: 999828
..... CPU clock speed is 1696.507 MHz.
..... host bus clock speed is 999.828 MHz.
There is no functional change to the LAPIC calibration here, beyond the
printing format changes.
[ bp: - Massage commit message
- Figures it should apply this patch about ~4 years later
- Massage it into the current code ]
Suggested-by: Markus Napierkowski <markus.napierkowski@cyberus-technology.de>
Signed-off-by: Julian Stecklina <julian.stecklina@cyberus-technology.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20211030142148.143261-1-js@alien8.de
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.