Re: [PATCH v9 06/19] ACPI: processor: Move checks and availability of acpi_processor earlier

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Tue, 7 May 2024 21:04:26 +0200
"Rafael J. Wysocki" <rafael@kernel.org> wrote:

> On Tue, Apr 30, 2024 at 4:27 PM Jonathan Cameron
> <Jonathan.Cameron@huawei.com> 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@huawei.com>  
> 
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> One nit below.

Thanks.  Given timing, this is looking like 6.11 material.
I'll tidy this up and post a v10 in a couple of weeks (so around
rc1 time). Maybe we'll pick up some more tags for the ARM
specific bits in the meantime.

Thanks for all your help!

Jonathan

> 
> > ---
> > v9: Add back a blank line accidentally removed in code move.
> >     Fix up error returns so that the new cleanup in processor_add()
> >     is triggered on detection of the bios bug.
> >     Combined with the previous 2 patches, should solve the leak
> >     that Gavin identified.
> > ---
> >  drivers/acpi/acpi_processor.c | 80 +++++++++++++++++++++--------------
> >  1 file changed, 49 insertions(+), 31 deletions(-)
> >
> > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> > index 16e36e55a560..4a79b42d649e 100644
> > --- a/drivers/acpi/acpi_processor.c
> > +++ b/drivers/acpi/acpi_processor.c
> > @@ -183,8 +183,38 @@ static void __init acpi_pcc_cpufreq_init(void) {}
> >  #endif /* CONFIG_X86 */
> >
> >  /* Initialization */
> > +static DEFINE_PER_CPU(void *, processor_device_array);
> > +
> > +static bool 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);
> > +               return false;
> > +       }
> > +       /*
> > +        * processor_device_array is not cleared on errors to allow buggy BIOS
> > +        * checks.
> > +        */
> > +       per_cpu(processor_device_array, pr->id) = device;
> > +       per_cpu(processors, pr->id) = pr;
> > +
> > +       return true;
> > +}
> > +
> >  #ifdef CONFIG_ACPI_HOTPLUG_CPU
> > -static int acpi_processor_hotadd_init(struct acpi_processor *pr)
> > +static int acpi_processor_hotadd_init(struct acpi_processor *pr,
> > +                                     struct acpi_device *device)
> >  {
> >         int ret;
> >
> > @@ -198,8 +228,16 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr)
> >         if (ret)
> >                 goto out;
> >
> > +       if (!acpi_processor_set_per_cpu(pr, device)) {
> > +               ret = -EINVAL;
> > +               acpi_unmap_cpu(pr->id);
> > +               goto out;
> > +       }
> > +
> >         ret = arch_register_cpu(pr->id);
> >         if (ret) {
> > +               /* Leave the processor device array in place to detect buggy bios */
> > +               per_cpu(processors, pr->id) = NULL;
> >                 acpi_unmap_cpu(pr->id);
> >                 goto out;
> >         }
> > @@ -217,7 +255,8 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr)
> >         return ret;
> >  }
> >  #else
> > -static inline int acpi_processor_hotadd_init(struct acpi_processor *pr)
> > +static inline int acpi_processor_hotadd_init(struct acpi_processor *pr,
> > +                                            struct acpi_device *device)
> >  {
> >         return -ENODEV;
> >  }
> > @@ -316,10 +355,13 @@ static int acpi_processor_get_info(struct acpi_device *device)
> >          *  because cpuid <-> apicid mapping is persistent now.
> >          */
> >         if (invalid_logical_cpuid(pr->id) || !cpu_present(pr->id)) {
> > -               int ret = acpi_processor_hotadd_init(pr);
> > +               int ret = acpi_processor_hotadd_init(pr, device);
> >
> >                 if (ret)
> >                         return ret;
> > +       } else {
> > +               if (!acpi_processor_set_per_cpu(pr, device))
> > +                       return -EINVAL;
> >         }  
> 
> This looks a bit odd.
> 
> I would make acpi_processor_set_per_cpu() return 0 on success and
> -EINVAL on failure and the above would become
> 
> if (invalid_logical_cpuid(pr->id) || !cpu_present(pr->id))
>          ret = acpi_processor_hotadd_init(pr, device);
> else
>         ret = acpi_processor_set_per_cpu(pr, device);
> 
> if (ret)
>         return ret;
> 
> (and of course ret needs to be defined at the beginning of the function).
> 
> >
> >         /*
> > @@ -365,8 +407,6 @@ static int acpi_processor_get_info(struct acpi_device *device)
> >   * (cpu_data(cpu)) values, like CPU feature flags, family, model, etc.
> >   * Such things have to be put in and set up by the processor driver's .probe().
> >   */
> > -static DEFINE_PER_CPU(void *, processor_device_array);
> > -
> >  static int acpi_processor_add(struct acpi_device *device,
> >                                         const struct acpi_device_id *id)
> >  {
> > @@ -395,28 +435,6 @@ static int acpi_processor_add(struct acpi_device *device,
> >         if (result) /* Processor is not physically present or unavailable */
> >                 goto err_clear_driver_data;
> >
> > -       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. */
> > -               goto err_clear_driver_data;
> > -       }
> > -       /*
> > -        * processor_device_array is not cleared on errors to allow buggy BIOS
> > -        * checks.
> > -        */
> > -       per_cpu(processor_device_array, pr->id) = device;
> > -       per_cpu(processors, pr->id) = pr;
> > -
> >         dev = get_cpu_device(pr->id);
> >         if (!dev) {
> >                 result = -ENODEV;
> > @@ -470,10 +488,6 @@ static void acpi_processor_remove(struct acpi_device *device)
> >         device_release_driver(pr->dev);
> >         acpi_unbind_one(pr->dev);
> >
> > -       /* Clean up. */
> > -       per_cpu(processor_device_array, pr->id) = NULL;
> > -       per_cpu(processors, pr->id) = NULL;
> > -
> >         cpu_maps_update_begin();
> >         cpus_write_lock();
> >
> > @@ -481,6 +495,10 @@ static void acpi_processor_remove(struct acpi_device *device)
> >         arch_unregister_cpu(pr->id);
> >         acpi_unmap_cpu(pr->id);
> >
> > +       /* Clean up. */
> > +       per_cpu(processor_device_array, pr->id) = NULL;
> > +       per_cpu(processors, pr->id) = NULL;
> > +
> >         cpus_write_unlock();
> >         cpu_maps_update_done();
> >
> > --
> > 2.39.2
> >