Record MPIDR for all started cores to table and use this table as link
between arbitrarily assigned cpuid and real system position of given core.
MFC after: 1 month
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Will this still work on the Juno where the boot cpu is not the first CPU in the dtb?
| sys/arm64/arm64/mp_machdep.c | ||
|---|---|---|
| 128 | You could put this into the pcpu structure. | |
| 453 | You should use CPU_AFF_MASK. We should have used it previously, I'm not sure why it wasn't. | |
| 471 | Extra space? | |
| 506 | This looks broken, it doesn't increment the cpu id for the boot CPU. I think it would be safer to put this check into start_cpu. | |
| 543 | Extra newline | |
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Boot CPU have always cpuid 0 so yes, it boots (i hope). I have disordered cpus nodes in my DTS and all looks OK.
| sys/arm64/arm64/mp_machdep.c | ||
|---|---|---|
| 128 | Nope, in view of D13864 we must be able to access this array before we known valid cpuid. But having a MPIDR also in pcpu structure doesn't sound bad. | |
| 453 | Yep, thanks. I missed CPU_AFF_MASK completely. | |
| 506 | The boot core have always cpuid=0 , so skipping it here is OK. But I forgot change initialization of 'cores' variable to 1 (at line 534 in new file). I will fix this in next version. | |
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Update to the final version. r359280 removed the need to access the cpu_mpidr table from the assembler. So eliminate it and insert the mpidr field into the pcpu structure as originally requested.
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Will this reorder the CPU IDs? One reason for the previous scheme because at least one Arm CPU has 4 little CPUs and 2 big. As it booted on the first big this would be CPU 4 in the DTB. By rotating we can keep the big CPUs together.
My preference would be to allow booting from pcpu[4], but haven't had the time to audit the code to check it doesn't hard code the boot CPU is 0.
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Yes, it changes CPU IDs. (For FDT case only. I assume that ACPI must always start on CPU0, even if I didn't find it in standard).
Please take in account that"
- actual FreeBSD must start on CPU0. imho, Nathan tried to fix this two/three years ago without success.
- numbering of CPUs in FDT is creative - is typically sequential, but some DT uses sparse numbering inspired by MPIDR. (see https://svnweb.freebsd.org/base/head/sys/gnu/dts/arm64/freescale/fsl-lx2160a.dtsi?revision=361848&view=markup#l160 )
- renumbering in original code also failed if the boot processor was not the first in the cluster.
By all this, I think that we should take CPU ID as arbitrary value, without any relationship to physical topology and topology itself should be presented by cpu_topo().And other consumers (like GIC, scheduler, NUMA...) should build its own cpu_sets for given functionality. I don't see possibility how to represent all this by single number.