Sean Christopherson 78bba966ee KVM: x86: Hide RDTSCP and RDPID if MSR_TSC_AUX probing failed
If probing MSR_TSC_AUX failed, hide RDTSCP and RDPID, and WARN if either
feature was reported as supported.  In theory, such a scenario should
never happen as both Intel and AMD state that MSR_TSC_AUX is available if
RDTSCP or RDPID is supported.  But, KVM injects #GP on MSR_TSC_AUX
accesses if probing failed, faults on WRMSR(MSR_TSC_AUX) may be fatal to
the guest (because they happen during early CPU bringup), and KVM itself
has effectively misreported RDPID support in the past.

Note, this also has the happy side effect of omitting MSR_TSC_AUX from
the list of MSRs that are exposed to userspace if probing the MSR fails.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-16-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-05-07 06:06:19 -04:00
2021-01-24 14:27:20 +01:00

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.
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