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Reject KVM if entry '0' in the host's IA32_PAT MSR is not programmed to writeback (WB) memtype. KVM subtly relies on IA32_PAT entry '0' to be programmed to WB by leaving the PAT bits in shadow paging and NPT SPTEs as '0'. If something other than WB is in PAT[0], at _best_ guests will suffer very poor performance, and at worst KVM will crash the system by breaking cache-coherency expecations (e.g. using WC for guest memory). Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20220715230016.3762909-2-seanjc@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.