Date: Tue, 30 Apr 2019 14:04:46 -0700 From: Mark Millard <marklmi@yahoo.com> To: Justin Hibbits <chmeeedalf@gmail.com>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Do non-PowerMac G5 powerpc64's ever get any slb faults in cpudep_ap_bootstrap? Message-ID: <F14FF29E-836E-4926-B432-2662C8951FCD@yahoo.com>
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Justin wrote in a bugzilla comment: > I'm trying to understand why Mark's SLB hack is necessary, > since it should logically be necessary on any other AIM-architecture = platform, > including my POWER9, so I'm really confused. Unfortunately, my G5 no = longer > works, and actually died shortly before I committed the change that = reportedly > broke G5s. I was/still am hoping that someone could go beyond Mark's = diving, > and determine just why the APs can't handle SLB faults at that point = in the > boot process, because they really should be able to. Could you find out if the AIM-ish powerpc64 contexts that you have access to ever seem get slb-miss faults in the pc_curpcb dereference in cpudep_ap_bootstrap 's: sp =3D pcpup->pc_curpcb->pcb_sp ? If they do, they are handled or you would see some effect. But,=20 are they even happening? If they are not happening, that could be a difference with the G5s. I ask for such, in part because of . . . The old VM_MAX_KERNEL_ADDRESS value avoiding the issue on G5s seems to be simply that the G5s were never getting the slb misses at that line when the old value was in use. (In other words, I expect that the change exposed a long-standing problem that was accidentally avoided until the change.) Unfortunately, I'm limited to G5s and you are limited to non-G5s. I can not check if other contexts are getting slb-misses in the same place or not but you might be able to. (But how?) I've not figured out anything beyond code-inspection for tracking down what happens for the slb-miss at that specific place when such happens on the G5's. So far I've not come up with any potentially useful ideas. =3D=3D=3D Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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