Thanks Lorenzo for pulling out the old thread. So just to make sure my understanding is correct from the discussion on that thread, below is not a preferred approach.
"If CPUs are marked as disabled in the devicetree, make sure they do not exist in the system CPU information and CPU topology information." The reason is because - "The meaning of disabled for cpus in ePAPR is that the cpu is offline (i.e. in a spinloop or wfi), not that the cpu is unavailable." Preferred approach is - "Since with this approach the DT should change anyway if on different > hardware devices based on the same chip you want to allow booting a > different number of CPUs, why do not we remove the cpu nodes instead of > disabling them" Thanks Rohit ________________________________________ From: Lorenzo Pieralisi <[email protected]> Sent: Thursday, April 26, 2018 3:18 AM To: Catalin Marinas; Rohit Khanna Cc: [email protected]; [email protected]; Thierry Reding; Alexander Van Brunt; Bo Yan; Jason Sequeira; Mark Rutland Subject: Re: [PATCH] arm64: skip cpu nodes marked as disabled in DT On Thu, Apr 26, 2018 at 08:25:14AM +0100, Catalin Marinas wrote: > On Wed, Apr 25, 2018 at 11:36:06PM +0000, Rohit Khanna wrote: > > Adding few other folks. > > It looks fine to me but cc'ing Mark and Lorenzo (and it should have been > posted on [email protected]). > > > From: Rohit Khanna > > Sent: Wednesday, April 25, 2018 4:08 PM > > To: [email protected]; [email protected] > > Cc: [email protected]; Rohit Khanna > > Subject: [PATCH] arm64: skip cpu nodes marked as disabled in DT > > > > Skip the CPU nodes that are marked as disabled in DT. > > > > Bug 1828570 That's not information that can be used in its current form, which bug-tracking system ? > > Signed-off-by: Rohit Khanna <[email protected]> > > Reviewed-on: http://git-master/r/1245333 If it is a public mailing list discussion the Link: tag and the lkml redirector should be used, I do not know what the redirector used here is though. Process is defined here: https://www.kernel.org/doc/html/latest/process/submitting-patches.html > > Reviewed-by: Alexander Van Brunt <[email protected]> > > --- > > arch/arm64/kernel/smp.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > > index f3e2e3aec0b0..2b4371b0948d 100644 > > --- a/arch/arm64/kernel/smp.c > > +++ b/arch/arm64/kernel/smp.c > > @@ -578,6 +578,10 @@ static void __init of_parse_and_init_cpus(void) > > for_each_node_by_type(dn, "cpu") { > > u64 hwid = of_get_cpu_mpidr(dn); > > > > + /* Check to see if the cpu is disabled */ > > + if (!of_device_is_available(dn)) > > + goto next; > > + This was discussed a long time ago and kind of dropped - I digged the thread out of archives for everyone's information: http://lists.infradead.org/pipermail/linux-arm-kernel/2013-June/174324.html Lorenzo
