On Mon, 22 Apr 2024 20:56:55 +0200
"Rafael J. Wysocki" <rafael@xxxxxxxxxx> wrote:
> On Thu, Apr 18, 2024 at 3:56 PM Jonathan Cameron
> <Jonathan.Cameron@xxxxxxxxxx> wrote:
> >
> > Make the per_cpu(processors, cpu) entries available earlier so that
> > they are available in arch_register_cpu() as ARM64 will need access
> > to the acpi_handle to distinguish between acpi_processor_add()
> > and earlier registration attempts (which will fail as _STA cannot
> > be checked).
> >
> > Reorder the remove flow to clear this per_cpu() after
> > arch_unregister_cpu() has completed, allowing it to be used in
> > there as well.
> >
> > Note that on x86 for the CPU hotplug case, the pr->id prior to
> > acpi_map_cpu() may be invalid. Thus the per_cpu() structures
> > must be initialized after that call or after checking the ID
> > is valid (not hotplug path).
> >
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> > ---
> > v7: Swap order with acpi_unmap_cpu() in acpi_processor_remove()
> > to keep it in reverse order of the setup path. (thanks Salil)
> > Fix an issue with placement of CONFIG_ACPI_HOTPLUG_CPU guards.
> > v6: As per discussion in v5 thread, don't use the cpu->dev and
> > make this data available earlier by moving the assignment checks
> > int acpi_processor_get_info().
> > ---
> > drivers/acpi/acpi_processor.c | 78 +++++++++++++++++++++--------------
> > 1 file changed, 46 insertions(+), 32 deletions(-)
> >
> > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> > index ba0a6f0ac841..ac7ddb30f10e 100644
> > --- a/drivers/acpi/acpi_processor.c
> > +++ b/drivers/acpi/acpi_processor.c
> > @@ -183,8 +183,36 @@ static void __init acpi_pcc_cpufreq_init(void) {}
> > #endif /* CONFIG_X86 */
> >
> > /* Initialization */
> > +static DEFINE_PER_CPU(void *, processor_device_array);
> > +
> > +static void acpi_processor_set_per_cpu(struct acpi_processor *pr,
> > + struct acpi_device *device)
> > +{
> > + BUG_ON(pr->id >= nr_cpu_ids);
> > + /*
> > + * Buggy BIOS check.
> > + * ACPI id of processors can be reported wrongly by the BIOS.
> > + * Don't trust it blindly
> > + */
> > + if (per_cpu(processor_device_array, pr->id) != NULL &&
> > + per_cpu(processor_device_array, pr->id) != device) {
> > + dev_warn(&device->dev,
> > + "BIOS reported wrong ACPI id %d for the processor\n",
> > + pr->id);
> > + /* Give up, but do not abort the namespace scan. */
> > + return;
>
> In this case the caller should make acpi_pricessor_add() return 0, I
> think, because otherwise it will attempt to acpi_bind_one() "pr" to
> "device" which will confuse things.
>
> So I would make this return false to indicate that.
>
> Or just fold it into the caller and do the error handling there.
The bios bug mentioned in reply to patch 14 (DSDT entries for non existent CPUs
that have no _STA entries) showed me that we need to know if this succeeded
(I'd not read this at that point).
I'll make it return a bool to say this succeeded and in both call sites
return 0 if not to deal with the bios bug here. Making sure not to clear
the per_cpu() structures unless this we get past that call. If we do
and arch_register_cpu() fails we need to clear these two IDs.
Doing so means that acpi_processor_hotadd_init() is side effect free and
hence we can return in acpi_processor_get_info() which avoids the
need to clear pointers when we don't have a valid pr->id to do it with.
So fully agree we need to bail out properly if this fails.
Jonathan
