Hi Julien, > On 22 Mar 2022, at 10:16, Julien Grall <jul...@xen.org> wrote: > > Hi, > > On 22/03/2022 08:47, Bertrand Marquis wrote: >> Hi Julien, >>> On 22 Mar 2022, at 09:35, Bertrand Marquis <bertrand.marq...@arm.com> wrote: >>> >>> Hi Julien, >>> >>>> On 21 Mar 2022, at 18:44, Julien Grall <jul...@xen.org> wrote: >>>> >>>> Hi Bertrand, >>>> >>>> On 21/03/2022 17:19, Bertrand Marquis wrote: >>>>>> On 21 Mar 2022, at 17:36, Julien Grall <jul...@xen.org> wrote: >>>>>>> So I don’t know why on x86 we must have cpu0 in cpupool0, maybe x86 >>>>>>> maintainer have more knowledge about that and >>>>>>> I can put a comment here. >>>>>> >>>>>> On Arm, we are not yet supporting all the CPU features that x86 supports >>>>>> (e.g. CPU hotplug, suspend/resume...). So I a am bit concerned that the >>>>>> restriction is just not there yet (or possibly hidden). >>>>>> >>>>>> Therefore, before lifting the restriction on Arm (and other arch), I >>>>>> would like us to understand why it is necessary on x86. >>>>>> >>>>>> We may not have the answer quickly, so is it going to be a problem to >>>>>> keep the restriction on Arm? >>>>> I am ok to keep the limitation to have dom0 always running on cpu0. >>>>> Only limitation I can see is that on a big little system, dom0 needs to >>>>> stay on the type of core of the first booted core. >>>> >>>> Where does this limitation come from? >>> >>> If dom0 must run on core0 and core0 is Little then you cannot build a >>> system where dom0 is running on big cores. >>> If the limitation is not there, you can build such a configuration without >>> any dependency to the boot core type. >> This might not be completely clear so let me rephrase: >> In the current system: >> - dom0 must run on cpupool-0 > > I don't think we need this restriction. In fact, with this series it will > become more a problem because the cpupool ID will based on how we parse the > Device-Tree. > > So for dom0, we need to specify explicitely the cpupool to be used. > >> - cpupool-0 must contain the boot core >> - consequence: dom0 must run on the boot core >> If boot core is little, you cannot build as system where dom0 runs only on >> the big cores. >> Removing the second limitation (which is not required on arm) is making it >> possible. > > IMHO removing the second restriction is a lot more risky than removing the > first one.
So keeping boot core in cpupool-0 but allow Dom-0 to be in any pool. Interesting, we will check that. Cheers Bertrand > > Cheers, > > -- > Julien Grall
