by Jonathan Cameron

[permalink] [raw]

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

On Tue, 7 May 2024 21:04:26 +0200
"Rafael J. Wysocki" <[email protected]> wrote:

> On Tue, Apr 30, 2024 at 4:27 PM Jonathan Cameron
> <[email protected]> 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 <[email protected]>
>
> Acked-by: Rafael J. Wysocki <[email protected]>
>
> 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
> >