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bb9dc85908
Disable LBR virtualization if the CPU doesn't support callstacks, which were introduced in HSW (see commite9d7f7cd97("perf/x86/intel: Add basic Haswell LBR call stack support"), as KVM unconditionally configures the perf LBR event with PERF_SAMPLE_BRANCH_CALL_STACK, i.e. LBR virtualization always fails on pre-HSW CPUs. Simply disable LBR support on such CPUs, as it has never worked, i.e. there is no risk of breaking an existing setup, and figuring out a way to performantly context switch LBRs on old CPUs is not worth the effort. Fixes:be635e34c2("KVM: vmx/pmu: Expose LBR_FMT in the MSR_IA32_PERF_CAPABILITIES") Cc: Mingwei Zhang <mizhang@google.com> Cc: Jim Mattson <jmattson@google.com> Tested-by: Mingwei Zhang <mizhang@google.com> Link: https://lore.kernel.org/r/20240307011344.835640-4-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 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.