Re: [PATCH v8 04/16] ACPI: processor: Move checks and availability of acpi_processor earlier

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On 4/26/24 23:51, Jonathan Cameron 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>

---
v8: On buggy bios detection when setting per_cpu structures
     do not carry on.
     Fix up the clearing of per cpu structures to remove unwanted
     side effects and ensure an error code isn't use to reference them.
---
  drivers/acpi/acpi_processor.c | 79 +++++++++++++++++++++--------------
  1 file changed, 48 insertions(+), 31 deletions(-)

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index ba0a6f0ac841..3b180e21f325 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);

One blank line after BUG_ON() if we need to follow original implementation.

+	/*
+	 * 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. */

It depends on how the return value is handled by the caller if the namespace
is continued to be scanned. The caller can be acpi_processor_hotadd_init()
and acpi_processor_get_info() after this patch is applied. So I think this
specific comment need to be moved to the caller.

Besides, it seems acpi_processor_set_per_cpu() isn't properly called and
memory leakage can happen. More details are given below.

+		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 +228,15 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr)
  	if (ret)
  		goto out;
+ if (!acpi_processor_set_per_cpu(pr, device)) {
+		acpi_unmap_cpu(pr->id);
+		goto out;
+	}
+

With the 'goto out', zero is returned from acpi_processor_hotadd_init() to acpi_processor_get_info().
The zero return value is carried from acpi_map_cpu() in acpi_processor_hotadd_init(). If I'm correct,
we need return errno from acpi_processor_get_info() to acpi_processor_add() so that cleanup can be
done. For example, the cleanup corresponding to the 'err' tag can be done in acpi_processor_add().
Otherwise, we will have memory leakage.

  	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 +254,8 @@ 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 +354,13 @@ 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 0;
  	}

For non-hotplug case, we still need pass the error to acpi_processor_add() so that
cleanup corresponding 'err' tag can be done. Otherwise, we will have memory leakage.

  	/*
@@ -365,8 +406,6 @@ 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 +434,6 @@ static int acpi_processor_add(struct acpi_device *device,
  	if (result) /* Processor is not physically present or unavailable */
  		return 0;
- 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;
-	}
-	/*
-	 * 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;
@@ -469,10 +486,6 @@ 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();
@@ -480,6 +493,10 @@ 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();

Thanks,
Gavin





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