On 24/05/18 16:12, Jan Beulich wrote: >>>> On 22.05.18 at 13:20, <andrew.coop...@citrix.com> wrote: >> The main purpose of this change is to allow us to set a specific MSR value, >> without needing to know whether there is already a load/save list slot for >> it. >> Previously, callers wanting this property needed to call both vmx_add_*_msr() >> and vmx_write_*_msr() to cover both cases. >> >> As a result of this API improvement, the default value for guest MSRs need >> not >> be 0, and the default for host MSRs need not be passed via hardware register. >> In practice, this cleans up the VPMU allocation logic, and avoids an MSR read >> as part of vcpu construction. > But this also means: If there already is such an entry, the previous value > will > now be blindly overwritten. Are you sure this is always what is wanted?
You are correct. This will end up resetting the LBR MSRs whenever the guest writes to MSR_DEBUGCTL. Overall, this behaviour is the more useful for callers, so I'll adjust the MSR_DEBUGCTL case to only ever try inserting them once. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
