Messages in this thread | | | Subject | Re: [PATCH] x86/smpboot: Remove 486-isms from the modern AP boot path | From | Andrew Cooper <> | Date | Wed, 1 Apr 2020 23:30:10 +0100 |
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On 01/04/2020 00:35, Maciej W. Rozycki wrote: > On Wed, 25 Mar 2020, Thomas Gleixner wrote: > >>>> @@ -1118,7 +1121,7 @@ static int do_boot_cpu(int apicid, int cpu, >>>> struct task_struct *idle, >>>> } >>>> } >>>> >>>> - if (x86_platform.legacy.warm_reset) { >>>> + if (!APIC_INTEGRATED(boot_cpu_apic_version)) { >>>> /* >>>> * Cleanup possible dangling ends... >>>> */ >>> We don't support SMP on 486 and haven't for a very long time. Is there >>> any reason to retain that code at all? >> Not that I'm aware off. > For the record: this code is for Pentium really, covering original P5 > systems, which lacked integrated APIC, as well as P54C systems that went > beyond dual (e.g. ALR made quad-SMP P54C systems). They all used external > i82489DX APICs for SMP support. Few were ever manufactured and getting > across one let alone running Linux might be tough these days. I never > managed to get one for myself, which would have been helpful for > maintaining this code. > > Even though we supported them by spec I believe we never actually ran MP > on any 486 SMP system (Alan Cox might be able to straighten me out on > this); none that I know of implemented the MPS even though actual hardware > might have used the APIC architecture. Compaq had its competing solution > for 486 and newer SMP, actually deployed, the name of which I long forgot. > We never supported it due to the lack of documentation combined with the > lack of enough incentive for someone to reverse-engineer it.
:)
I chose "486-ism" based on what the MP spec said about external vs integrated Local APICs. I can't claim to have any experience of those days.
I guess given v2 of the patch, I guess this should become "Remove external-LAPIC support from the AP boot path" ?
~Andrew
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