On Wed, Nov 20, 2019 at 06:40:06PM +0100, Paolo Bonzini wrote: > On 20/11/19 17:49, Eduardo Habkost wrote: > > One of the mitigation methods for TAA[1] is to disable TSX > > support on the host system. Linux added a mechanism to disable > > TSX globally through the kernel command line, and many Linux > > distributions now default to tsx=off. This makes existing CPU > > models that have HLE and RTM enabled not usable anymore. > > > > Add new versions of all CPU models that have the HLE and RTM > > features enabled, that can be used when TSX is disabled in the > > host system. > > What is the effect of this when using "-cpu CascadeLake-Server" and > upgrading QEMU? Would it automatically switch to the new version? If > so, would it be better to include a duplicate of the models (and if so, > that would conflict with my VMX features patch, which is also for 4.2).
It won't, because PCMachineClass::default_cpu_version==1 for all versioned PC machine-types, currently. The plan is to set default_cpu_version=CPU_VERSION_LATEST on pc-*-5.0 (or, more likely, 5.1). But this will happen only after libvirt starts resolving CPU model versions. See the "Runnability guarantee of CPU models" section at qemu-deprecated.texi. -- Eduardo
