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Expand the comment about what bits are and aren't checked when emulating PMC events in software. As pointed out by Jim, AMD's mask includes bits 35:32, which on Intel overlap with the IN_TX and IN_TXCP bits (32 and 33) as well as reserved bits (34 and 45). Checking The IN_TX* bits is actually correct, as it's safe to assert that the vCPU can't be in an HLE/RTM transaction if KVM is emulating an instruction, i.e. KVM *shouldn't count if either of those bits is set. For the reserved bits, KVM is has equal odds of being right if Intel adds new behavior, i.e. ignoring them is just as likely to be correct as checking them. Opportunistically explain *why* the other flags aren't checked. Suggested-by: Jim Mattson <jmattson@google.com> Link: https://lore.kernel.org/r/20231110022857.1273836-9-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>
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 Restructured Text 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.