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When using shadow paging, a CR3 switch in the guest results in a VM Exit. In the common case, that VM exit doesn't require much processing by KVM. However, it does acquire the MMU lock, which can start showing signs of contention under some workloads even on a 2 VCPU VM when the guest is using KPTI. Therefore, we add a fast path that avoids acquiring the MMU lock in the most common cases e.g. when switching back and forth between the kernel and user mode CR3s used by KPTI with no guest page table changes in between. For now, this fast path is implemented only for 64-bit guests and hosts to avoid the handling of PDPTEs, but it can be extended later to 32-bit guests and/or hosts as well. Signed-off-by: Junaid Shahid <junaids@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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.