On 28/06/18 14:35, Jan Beulich wrote: >>>> On 26.06.18 at 13:35, <andrew.coop...@citrix.com> wrote: >> --- a/xen/arch/x86/Kconfig >> +++ b/xen/arch/x86/Kconfig >> @@ -161,3 +161,24 @@ endmenu >> source "common/Kconfig" >> >> source "drivers/Kconfig" >> + >> +menu "Deprecated Functionality" >> + >> +config LEGACY_PV_LDT_PAGING >> + def_bool n >> + prompt "PV LDT Paging-out support" >> + ---help--- >> + For a very long time, the PV ABI has included the ability to page >> + out the LDT by transitioning its mapping to not-present. This >> + functionality is believed to only exist for the PV Windows XP port >> + which never came to anything. >> + >> + The implementation contains a vCPU scalability limitation in a >> + position which is prohibitively complicated to resolve. As the >> + feature is believed to be unused in practice, removing the feature >> + is the easiest remediation. >> + >> + If you discover a usecase which is broken by this option being off, >> + please contact xen-devel@lists.xenproject.org urgently. Baring >> + something unexpected, the code and this option will be removed. > I think it should be said here explicitly when (or to be precise, no earlier > than when) this is going to happen.
I'm open to suggests, but decided not to name a specific release (if only to avoid second-guessing our future numbering and release schedule). > I also think the security support status with the option enabled needs to > be clarified. Perhaps we'd go in stages: Introduce the (default off) option, > then (e.g. for 4.13) switch its use to security unsupported, and finally > drop the code (e.g. for 4.14). I presume you mean that we should hide it behind EXPERT at that point? What does the middle step gets us. If its going to be off by default and unable to be enabled by default, that is as good as deleted. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
