cbbd1aa891
Remove KVM's bogus restriction that the guest can't program an event whose
encoding matches an unsupported architectural event. The enumeration of
an architectural event only says that if a CPU supports an architectural
event, then the event can be programmed using the architectural encoding.
The enumeration does NOT say anything about the encoding when the CPU
doesn't report support the architectural event.
Preventing the guest from counting events whose encoding happens to match
an architectural event breaks existing functionality whenever Intel adds
an architectural encoding that was *ever* used for a CPU that doesn't
enumerate support for the architectural event, even if the encoding is for
the exact same event!
E.g. the architectural encoding for Top-Down Slots is 0x01a4. Broadwell
CPUs, which do not support the Top-Down Slots architectural event, 0x01a4
is a valid, model-specific event. Denying guest usage of 0x01a4 if/when
KVM adds support for Top-Down slots would break any Broadwell-based guest.
Reported-by: Kan Liang <kan.liang@linux.intel.com>
Closes: https://lore.kernel.org/all/2004baa6-b494-462c-a11f-8104ea152c6a@linux.intel.com
Fixes: a21864486f ("KVM: x86/pmu: Fix available_event_types check for REF_CPU_CYCLES event")
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-3-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.