Hi Lorenzo,

On 2014?01?22? 23:53, Lorenzo Pieralisi wrote:

On Fri, Jan 17, 2014 at 12:25:04PM +0000, Hanjun Guo wrote:

[...]

quoted

+/* map logic cpu id to physical GIC id */
+extern int arm_cpu_to_apicid[NR_CPUS];
+#define cpu_physical_id(cpu) arm_cpu_to_apicid[cpu]

Sudeep already commented on this, please update it accordingly.

Actually after some careful review of the ACPI code, I can't
update it as MPIDR here.

MPIDR can be the ACPI uid and NOT the GIC id, the mapping
of them are something like this in ACPI driver now:

logic cpu id <---> APIC Id (GIC ID) <---> ACPI uid (MPIDR on ARM)
but not logic cpu id <---> ACPI uid directly, you can refer to
the code of processor_core.c

So here I can only map GIC id to logical cpu id.

quoted

+
  #else	/* !CONFIG_ACPI */
  #define acpi_disabled 1		/* ACPI sometimes enabled on ARM */
  #define acpi_noirq 1		/* ACPI sometimes enabled on ARM */

diff --git a/drivers/acpi/plat/arm-core.c b/drivers/acpi/plat/arm-core.c
index 8ba3e6f..1d9b789 100644
--- a/drivers/acpi/plat/arm-core.c
+++ b/drivers/acpi/plat/arm-core.c

@@ -31,6 +31,7 @@
  #include <linux/smp.h>
  
  #include <asm/pgtable.h>
+#include <asm/cputype.h>
  
  /*
   * We never plan to use RSDT on arm/arm64 as its deprecated in spec but this

@@ -52,6 +53,13 @@ EXPORT_SYMBOL(acpi_pci_disabled);
   */
  static u64 acpi_lapic_addr __initdata;

Is this variable actually needed ?

Yes, needed for GIC initialization.

quoted

  
+/* available_cpus here means enabled cpu in MADT */
+static int available_cpus;

Ditto.

quoted

+
+/* Map logic cpu id to physical GIC id (physical CPU id). */
+int arm_cpu_to_apicid[NR_CPUS] = { [0 ... NR_CPUS-1] = -1 };
+static int boot_cpu_apic_id = -1;

Do we need all these variables ? I think we should reuse cpu_logical_map
data structures for that, it looks suspiciously familiar.

MPIDR is the different part. if we use MPIDR as GIC id, i think
we can reuse cpu_logical_map, but Sudeep suggested not
use MPIDR as GIC id.

quoted

  #define BAD_MADT_ENTRY(entry, end) (					\
  	(!entry) || (unsigned long)entry + sizeof(*entry) > end ||	\
  	((struct acpi_subtable_header *)entry)->length < sizeof(*entry))

@@ -132,6 +140,55 @@ static int __init acpi_parse_madt(struct acpi_table_header *table)
   * Please refer to chapter5.2.12.14/15 of ACPI 5.0
   */
  
+/**
+ * acpi_register_gic_cpu_interface - register a gic cpu interface and
+ * generates a logic cpu number
+ * @id: gic cpu interface id to register
+ * @enabled: this cpu is enabled or not
+ *
+ * Returns the logic cpu number which maps to the gic cpu interface
+ */
+static int acpi_register_gic_cpu_interface(int id, u8 enabled)
+{
+	int cpu;
+
+	if (id >= MAX_GIC_CPU_INTERFACE) {
+		pr_info(PREFIX "skipped apicid that is too big\n");
+		return -EINVAL;
+	}
+
+	total_cpus++;
+	if (!enabled)
+		return -EINVAL;
+
+	if (available_cpus >=  NR_CPUS) {
+		pr_warn(PREFIX "NR_CPUS limit of %d reached,"
+		" Processor %d/0x%x ignored.\n", NR_CPUS, total_cpus, id);
+		return -EINVAL;
+	}

Hmm...what if you are missing the boot CPU ? It is a worthy check.
Have a look at smp_init_cpus(), it does not bail out on cpu>= NR_CPUS
because you do want to make sure that the DT contains the boot CPU
node. Same logic applies.

Thanks, I will review he code you mentioned and find a solution
for ACPI part.

quoted

+
+	available_cpus++;
+

Is available_cpus != num_possible_cpus() ? It does not look like hence
available_cpus can go.

No, possible cpus include available cpus and disabled cpus
this is useful for ACPI based CPU hot-plug features.

quoted

+	/* allocate a logic cpu id for the new comer */
+	if (boot_cpu_apic_id == id) {
+		/*
+		 * boot_cpu_init() already hold bit 0 in cpu_present_mask
+		 * for BSP, no need to allocte again.
+		 */
+		cpu = 0;
+	} else {
+		cpu = cpumask_next_zero(-1, cpu_present_mask);
+	}
+
+	/* map the logic cpu id to APIC id */
+	arm_cpu_to_apicid[cpu] = id;
+
+	set_cpu_present(cpu, true);
+	set_cpu_possible(cpu, true);

This is getting nasty. Before adding this patch and previous ones we
need to put in place a method for the kernel to make a definite choice between
ACPI and DT and stick to that. We can't initialize the logical map twice
(which will happen if your DT has valid cpu nodes and a chosen node pointing
to proper ACPI tables) or even having some entries initialized from DT and
others by ACPI. It is a big fat no-no, please update the series accordingly.

really good catch here :)
so the problem here is that should we use both ACPI and DT in one system?

quoted

+
+	return cpu;
+}
+
  static int __init
  acpi_parse_gic(struct acpi_subtable_header *header, const unsigned long end)
  {

@@ -144,6 +201,16 @@ acpi_parse_gic(struct acpi_subtable_header *header, const unsigned long end)
  
  	acpi_table_print_madt_entry(header);
  
+	/*
+	 * We need to register disabled CPU as well to permit
+	 * counting disabled CPUs. This allows us to size
+	 * cpus_possible_map more accurately, to permit
+	 * to not preallocating memory for all NR_CPUS
+	 * when we use CPU hotplug.
+	 */
+	acpi_register_gic_cpu_interface(processor->gic_id,
+			processor->flags & ACPI_MADT_ENABLED);
+
  	return 0;
  }
  

@@ -186,6 +253,19 @@ static int __init acpi_parse_madt_gic_entries(void)
  		return count;
  	}
  
+#ifdef CONFIG_SMP
+	if (available_cpus == 0) {
+		pr_info(PREFIX "Found 0 CPUs; assuming 1\n");
+		arm_cpu_to_apicid[available_cpus] =
+			read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
+		available_cpus = 1;	/* We've got at least one of these */
+	}

I'd rather check the MADT for at least the boot cpu to present, if it is
not ACPI tables are horribly buggy and the kernel should barf on that.

quoted

+#endif
+
+	/* Make boot-up look pretty */
+	pr_info("%d CPUs available, %d CPUs total\n", available_cpus,
+		total_cpus);

Ok, now, how can we use the "disabled" CPUs == (total_cpus - available_cpus) ?

For cpus can be hot-added later when system is running.

Are we keeping track of them in the kernel at all ? It does not look
like, so I wonder whether we need this bit of info. I do not see why it
is pretty to know that there are disabled, aka unusable CPUs.

quoted

  	return 0;
  }
  

@@ -321,6 +401,9 @@ int __init early_acpi_boot_init(void)
  	if (acpi_disabled)
  		return -ENODEV;
  
+	/* Get the boot CPU's GIC cpu interface id before MADT parsing */
+	boot_cpu_apic_id = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;

See Sudeep's comment.

I will rework this part to get the GIC cpu interface id, not the MPIDR here.

Thanks
Hanjun