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For Intel, the guest PMU can be disabled via clearing the PMU CPUID. For AMD, all hw implementations support the base set of four performance counters, with current mainstream hardware indicating the presence of two additional counters via X86_FEATURE_PERFCTR_CORE. In the virtualized world, the AMD guest driver may detect the presence of at least one counter MSR. Most hypervisor vendors would introduce a module param (like lbrv for svm) to disable PMU for all guests. Another control proposal per-VM is to pass PMU disable information via MSR_IA32_PERF_CAPABILITIES or one bit in CPUID Fn4000_00[FF:00]. Both of methods require some guest-side changes, so a module parameter may not be sufficiently granular, but practical enough. Signed-off-by: Like Xu <likexu@tencent.com> Message-Id: <20211117080304.38989-1-likexu@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.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.