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Michael Ellerman
2a3d6553cb
Currently we use CPU_FTR_TM to decide if the CPU/kernel can support TM (Transactional Memory), and if it's true we advertise that to Qemu (or similar) via KVM_CAP_PPC_HTM. PPC_FEATURE2_HTM is the user-visible feature bit, which indicates that the CPU and kernel can support TM. Currently CPU_FTR_TM and PPC_FEATURE2_HTM always have the same value, either true or false, so using the former for KVM_CAP_PPC_HTM is correct. However some Power9 CPUs can operate in a mode where TM is enabled but TM suspended state is disabled. In this mode CPU_FTR_TM is true, but PPC_FEATURE2_HTM is false. Instead a different PPC_FEATURE2 bit is set, to indicate that this different mode of TM is available. It is not safe to let guests use TM as-is, when the CPU is in this mode. So to prevent that from happening, use PPC_FEATURE2_HTM to determine the value of KVM_CAP_PPC_HTM. Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.