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Date: Tue, 7 May 2024 21:04:26 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>, linux-pm@...r.kernel.org,
loongarch@...ts.linux.dev, linux-acpi@...r.kernel.org,
linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, x86@...nel.org,
Russell King <linux@...linux.org.uk>, "Rafael J . Wysocki" <rafael@...nel.org>,
Miguel Luis <miguel.luis@...cle.com>, James Morse <james.morse@....com>,
Salil Mehta <salil.mehta@...wei.com>, Jean-Philippe Brucker <jean-philippe@...aro.org>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
Hanjun Guo <guohanjun@...wei.com>, Gavin Shan <gshan@...hat.com>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, linuxarm@...wei.com,
justin.he@....com, jianyong.wu@....com
Subject: Re: [PATCH v9 06/19] ACPI: processor: Move checks and availability of
acpi_processor earlier
On Tue, Apr 30, 2024 at 4:27 PM Jonathan Cameron
<Jonathan.Cameron@...wei.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@...wei.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
One nit below.
> ---
> 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
>
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