On 26/11/2025 2:19 pm, Jan Beulich wrote: > On 26.11.2025 14:22, Andrew Cooper wrote: >> When re-scanning features, > What exactly do you mean with this, outside of XenServer (i.e. upstream)? The > only thing I can think of is recheck_cpu_features(), which calls > identify_cpu() > and hence init_amd(). Thus ... > >> forced caps are taken into account but unforced >> such as this are not. This causes BTC_NO to go missing, and for the system >> to >> appear to have lost features. > ... I don't really follow where features might be lost.
Well - it's a feature that we started upstreaming and I still hope to finish in some copious free time. Already upstream, we rescan the Raw CPU policy after microcode load. That has had fixes such as dis-engaging CPUID Masking/Overriding so the Raw policy comes out accurate. The next step (not upstream yet) is to regenerate the Host and Guest policies. I recently fixed a bug in XenServer's testing and noticed that the underlying logic had bit-rotted quite a bit, hence this series. The purpose is to be able to activate new features added by a late microcode load, such as new speculative defences, or simply provide new FOO_NO bits. ~Andrew
