On Fri, 27 Dec 2019, trueriver wrote: > Running a new install of Qubes r4.0.1 on an ultrabook based on the > m5-6Y54 processor / SOC. Xentop shows it as having only 2 cores. > > When the same machine boots into Debian on bare metal, with no BIOS > changes, top shows it as having four. > > The Intel spec is 2 cores running 4 threads, so the difference is > clearly about hyperthreading. > > Is it possible to get Xen in Qubes to enable hyperthreading? > > And if so how?
There's smt xen command-line parameter. > Are there any obvs pitfalls or technical issues to explain why Xen turns > it off? Yes, HT is turned off intentionally for security purposes. Some of the Intel CPU vulnerabilities demonstrated within the recent years depend on the side channels within the resources shared by the threads of the same physical core. Thus it's advisable to not enable it. -- i. -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/alpine.DEB.2.20.1912272328150.22137%40whs-18.cs.helsinki.fi.
