On Thu, 2017-10-12 at 11:58:54 UTC, Michael Ellerman wrote: > 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 <m...@ellerman.id.au>
Applied to powerpc next. https://git.kernel.org/powerpc/c/2a3d6553cbd791da4fb624c2500b45 cheers
