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To date, VMM-directed TSC synchronization and migration has been a bit messy. KVM has some baked-in heuristics around TSC writes to infer if the VMM is attempting to synchronize. This is problematic, as it depends on host userspace writing to the guest's TSC within 1 second of the last write. A much cleaner approach to configuring the guest's views of the TSC is to simply migrate the TSC offset for every vCPU. Offsets are idempotent, and thus not subject to change depending on when the VMM actually reads/writes values from/to KVM. The VMM can then read the TSC once with KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when the guest is paused. Cc: David Matlack <dmatlack@google.com> Cc: Sean Christopherson <seanjc@google.com> Signed-off-by: Oliver Upton <oupton@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210916181538.968978-8-oupton@google.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.