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Mostly-Inverted CPU-Core ordering
On Fri, 03 Apr 2026 08:34:48 +0200,
Jeremie Courreges-Anglas <jca@wxcvbn.org> wrote:
>
> On Sat, Mar 07, 2026 at 09:37:17AM +0100, Stefan Fritsch wrote:
> > On Fri, 6 Mar 2026, Theo de Raadt wrote:
> >
> > > > Not my area. Should this be committed?
> > >
> > > I am not sure why it hasn't been.
> > >
> >
> > AFAIK, it has only been tested on amd64, arm64, i386. The other
> > architectures need testing. And an ok would be nice.
>
> Apologies for the delay, Stefan!
>
> I guess you could have committed the diffs for architectures that have
> been tested already. Regarding the remaining architectures:
> - alpha: I'll try to test this with miod's help during this week-end
> - arm: no MP so no meaningful test possible
> - mips64: can't test right now but at least visa/kirill/kn have such hw
> - riscv64: GENERIC builds, GENERIC.MP runs (hw: Hifive Unmatched)
>
> All your changes look fine to me. ok jca@ for the architectures that
> have been tested and arm. ok for the rest when you get basic testing.
>
> cc'ing the relevant folks, here's the second/latest diff with
> !MULTIPROCESSOR fixes, for convenience.
>
This diff boots on my ER-4 and I used this diff to print CPU order
https://marc.info/?l=openbsd-tech&m=177287523800901&w=2
Difference between without diff and with diff is:
$ diff -uNar dmesg /var/run/dmesg.boot
--- dmesg Fri Apr 3 11:15:36 2026
+++ /var/run/dmesg.boot Fri Apr 3 11:27:21 2026
@@ -79,6 +79,6 @@
root on sd0a (d008e854197154dd.a) swap on sd0b dump on sd0b
WARNING: CHECK AND RESET THE DATE!
cpu 0
-cpu 3
-cpu 2
cpu 1
+cpu 2
+cpu 3
So, it make sense to me
> diff --git a/sys/arch/alpha/alpha/cpu.c b/sys/arch/alpha/alpha/cpu.c
> index 23b25c94219..38425f1d905 100644
> --- a/sys/arch/alpha/alpha/cpu.c
> +++ b/sys/arch/alpha/alpha/cpu.c
> @@ -419,7 +419,7 @@ cpu_announce_extensions(struct cpu_info *ci)
> void
> cpu_boot_secondary_processors(void)
> {
> - struct cpu_info *ci;
> + struct cpu_info *ci, *ci_last;
> u_long i;
>
> for (i = 0; i < ALPHA_MAXPROCS; i++) {
> @@ -434,8 +434,10 @@ cpu_boot_secondary_processors(void)
> /*
> * Link the processor into the list, and launch it.
> */
> - ci->ci_next = cpu_info_list->ci_next;
> - cpu_info_list->ci_next = ci;
> + ci_last = cpu_info_list;
> + while (ci_last->ci_next != NULL)
> + ci_last = ci_last->ci_next;
> + ci_last->ci_next = ci;
> atomic_setbits_ulong(&ci->ci_flags, CPUF_RUNNING);
> atomic_setbits_ulong(&cpus_running, (1UL << i));
> ncpus++;
> diff --git a/sys/arch/amd64/amd64/cpu.c b/sys/arch/amd64/amd64/cpu.c
> index 18cfb8d6377..4d56f320c33 100644
> --- a/sys/arch/amd64/amd64/cpu.c
> +++ b/sys/arch/amd64/amd64/cpu.c
> @@ -729,8 +729,11 @@ cpu_attach(struct device *parent, struct device *self, void *aux)
> sched_init_cpu(ci);
> ncpus++;
> if (ci->ci_flags & CPUF_PRESENT) {
> - ci->ci_next = cpu_info_list->ci_next;
> - cpu_info_list->ci_next = ci;
> + struct cpu_info *ci_last = cpu_info_list;
> +
> + while (ci_last->ci_next != NULL)
> + ci_last = ci_last->ci_next;
> + ci_last->ci_next = ci;
> }
> #else
> printf("%s: not started\n", sc->sc_dev.dv_xname);
> diff --git a/sys/arch/arm/arm/cpu.c b/sys/arch/arm/arm/cpu.c
> index f51404f73be..005211ba35f 100644
> --- a/sys/arch/arm/arm/cpu.c
> +++ b/sys/arch/arm/arm/cpu.c
> @@ -354,10 +354,14 @@ cpu_attach(struct device *parent, struct device *dev, void *aux)
> ci = &cpu_info_primary;
> ci->ci_flags |= CPUF_RUNNING | CPUF_PRESENT | CPUF_PRIMARY;
> } else {
> + struct cpu_info *ci_last;
> +
> ci = malloc(sizeof(*ci), M_DEVBUF, M_WAITOK | M_ZERO);
> cpu_info[dev->dv_unit] = ci;
> - ci->ci_next = cpu_info_list->ci_next;
> - cpu_info_list->ci_next = ci;
> + ci_last = cpu_info_list;
> + while (ci_last->ci_next != NULL)
> + ci_last = ci_last->ci_next;
> + ci_last->ci_next = ci;
> ci->ci_flags |= CPUF_AP;
> ncpus++;
> }
> diff --git a/sys/arch/arm64/arm64/cpu.c b/sys/arch/arm64/arm64/cpu.c
> index f9784e432db..8f59fc03e0f 100644
> --- a/sys/arch/arm64/arm64/cpu.c
> +++ b/sys/arch/arm64/arm64/cpu.c
> @@ -1481,6 +1481,7 @@ cpu_attach(struct device *parent, struct device *dev, void *aux)
> struct cpu_info *ci;
> void *kstack;
> #ifdef MULTIPROCESSOR
> + struct cpu_info *ci_last;
> uint64_t mpidr = READ_SPECIALREG(mpidr_el1);
> #endif
> uint32_t opp;
> @@ -1494,8 +1495,10 @@ cpu_attach(struct device *parent, struct device *dev, void *aux)
> } else {
> ci = malloc(sizeof(*ci), M_DEVBUF, M_WAITOK | M_ZERO);
> cpu_info[dev->dv_unit] = ci;
> - ci->ci_next = cpu_info_list->ci_next;
> - cpu_info_list->ci_next = ci;
> + ci_last = cpu_info_list;
> + while (ci_last->ci_next != NULL)
> + ci_last = ci_last->ci_next;
> + ci_last->ci_next = ci;
> ci->ci_flags |= CPUF_AP;
> ncpus++;
> }
> diff --git a/sys/arch/i386/i386/cpu.c b/sys/arch/i386/i386/cpu.c
> index c5f18dd4433..e3b4d7cc589 100644
> --- a/sys/arch/i386/i386/cpu.c
> +++ b/sys/arch/i386/i386/cpu.c
> @@ -234,6 +234,7 @@ cpu_attach(struct device *parent, struct device *self, void *aux)
> struct cpu_info *ci;
>
> #ifdef MULTIPROCESSOR
> + struct cpu_info *ci_last;
> int cpunum = sc->sc_dev.dv_unit;
> vaddr_t kstack;
> struct pcb *pcb;
> @@ -365,8 +366,10 @@ cpu_attach(struct device *parent, struct device *self, void *aux)
> identifycpu(ci);
> clockqueue_init(&ci->ci_queue);
> sched_init_cpu(ci);
> - ci->ci_next = cpu_info_list->ci_next;
> - cpu_info_list->ci_next = ci;
> + ci_last = cpu_info_list;
> + while (ci_last->ci_next != NULL)
> + ci_last = ci_last->ci_next;
> + ci_last->ci_next = ci;
> ncpus++;
> #endif
> break;
> diff --git a/sys/arch/mips64/mips64/cpu.c b/sys/arch/mips64/mips64/cpu.c
> index 040669d397b..fe45ce0970c 100644
> --- a/sys/arch/mips64/mips64/cpu.c
> +++ b/sys/arch/mips64/mips64/cpu.c
> @@ -95,9 +95,13 @@ cpuattach(struct device *parent, struct device *dev, void *aux)
> panic("unable to allocate cpu_info");
> }
> } else {
> + struct cpu_info *ci_last;
> +
> ci = &cpu_info_secondaries[cpuno - 1];
> - ci->ci_next = cpu_info_list->ci_next;
> - cpu_info_list->ci_next = ci;
> + ci_last = cpu_info_list;
> + while (ci_last->ci_next != NULL)
> + ci_last = ci_last->ci_next;
> + ci_last->ci_next = ci;
> ci->ci_flags |= CPUF_PRESENT;
> }
> #else
> diff --git a/sys/arch/riscv64/riscv64/cpu.c b/sys/arch/riscv64/riscv64/cpu.c
> index e8400d4eed3..1c2c2a1341c 100644
> --- a/sys/arch/riscv64/riscv64/cpu.c
> +++ b/sys/arch/riscv64/riscv64/cpu.c
> @@ -195,10 +195,14 @@ cpu_attach(struct device *parent, struct device *dev, void *aux)
> ci->ci_flags |= CPUF_RUNNING | CPUF_PRESENT | CPUF_PRIMARY;
> csr_set(sie, SIE_SSIE);
> } else {
> + struct cpu_info *ci_last;
> +
> ci = malloc(sizeof(*ci), M_DEVBUF, M_WAITOK | M_ZERO);
> cpu_info[dev->dv_unit] = ci;
> - ci->ci_next = cpu_info_list->ci_next;
> - cpu_info_list->ci_next = ci;
> + ci_last = cpu_info_list;
> + while (ci_last->ci_next != NULL)
> + ci_last = ci_last->ci_next;
> + ci_last->ci_next = ci;
> ci->ci_flags |= CPUF_AP;
> ncpus++;
> }
>
>
>
> --
> jca
--
wbr, Kirill
Mostly-Inverted CPU-Core ordering