[PATCH v2 06/18] ARM64 / ACPI: Parse MADT to map logical cpu to MPIDR and get cpu_possible/present_map

Hi Sudeep,

On 2014-8-19 2:33, Sudeep Holla wrote:

On 04/08/14 16:28, Hanjun Guo wrote:

quoted

MADT contains the information for MPIDR which is essential for
SMP initialization, parse the GIC cpu interface structures to
get the MPIDR value and map it to cpu_logical_map(), and add
enabled cpu with valid MPIDR into cpu_possible_map and
cpu_present_map.

Signed-off-by: Hanjun Guo <redacted>
Signed-off-by: Tomasz Nowicki <redacted>
---
  arch/arm64/include/asm/acpi.h |    2 +
  arch/arm64/kernel/acpi.c      |  129 ++++++++++++++++++++++++++++++++++++++++-
  arch/arm64/kernel/smp.c       |   10 +++-
  3 files changed, 138 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index 6e04868..e877967 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h

@@ -64,6 +64,8 @@ static inline void arch_fix_phys_package_id(int num, u32

slot) { }
  extern int (*acpi_suspend_lowlevel)(void);
  #define acpi_wakeup_address 0

+#define MAX_GIC_CPU_INTERFACE 65535
+

Did you get this information from GIC specification ?

Actually not. since MAX_GIC_CPU_INTERFACE represents the maximum GIC CPU
interfaces (CPUs) entries in MADT, so I use a number big enough to represent max
CPUs in the system.

IIUC you are trying to represent max number of interrupt controller
entries MADT can possibly have. So, I had suggested to change the name
like MAX_MADT_INTERRUPT_CONTROLLER_ENTRIES so that it is not GIC specific.

Will INTERRUPT_CONTROLLER confuse people? There is only one GIC redistributor
(some people regard it as interrupt controller) in ARM system, if we use
INTERRUPT_CONTROLLER people will regard it as multi-redistributors in the
system, I think GIC_CPU_INTERFACE would be better, what do you think?

quoted

  #endif /* CONFIG_ACPI */

  #endif /*_ASM_ACPI_H*/

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index 69a315d..9e07d99 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c

@@ -22,6 +22,9 @@
  #include <linux/bootmem.h>
  #include <linux/smp.h>

+#include <asm/smp_plat.h>
+#include <asm/cputype.h>
+
  int acpi_noirq;            /* skip ACPI IRQ initialization */
  int acpi_disabled;
  EXPORT_SYMBOL(acpi_disabled);

@@ -29,6 +32,8 @@ EXPORT_SYMBOL(acpi_disabled);
  int acpi_pci_disabled;        /* skip ACPI PCI scan and IRQ initialization */
  EXPORT_SYMBOL(acpi_pci_disabled);

+static int enabled_cpus;    /* Processors (GICC) with enabled flag in MADT */
+
  /*
   * __acpi_map_table() will be called before page_init(), so early_ioremap()
   * or early_memremap() should be called here to for ACPI table mapping.

@@ -49,6 +54,122 @@ void __init __acpi_unmap_table(char *map, unsigned long size)
      early_memunmap(map, size);
  }

+/**
+ * acpi_register_gic_cpu_interface - register a gic cpu interface and
+ * generates a logical cpu number
+ * @mpidr: CPU's hardware id to register, MPIDR represented in MADT
+ * @enabled: this cpu is enabled or not
+ *
+ * Returns the logical cpu number which maps to the gic cpu interface
+ */
+static int acpi_register_gic_cpu_interface(u64 mpidr, u8 enabled)
+{

IMO the function name gives me a wrong idea that you are registering
something with GIC. How about acpi_map_gic_cpu_interface ?

Great, acpi_map_gic_cpu_interface is better.

quoted

+    int cpu;
+
+    if (mpidr == INVALID_HWID) {
+        pr_info("Skip invalid cpu hardware ID\n");
+        return -EINVAL;
+    }
+
+    total_cpus++;
+    if (!enabled)
+        return -EINVAL;
+
+    if (enabled_cpus >=  NR_CPUS) {
+        pr_warn("NR_CPUS limit of %d reached, Processor %d/0x%llx ignored.\n",
+            NR_CPUS, total_cpus, mpidr);
+        return -EINVAL;
+    }
+
+    /* If it is the first CPU, no need to check duplicate MPIDRs */
+    if (!enabled_cpus)
+        goto skip_mpidr_check;
+
+    /*
+     * Duplicate MPIDRs are a recipe for disaster. Scan
+     * all initialized entries and check for
+     * duplicates. If any is found just ignore the CPU.
+     */
+    for_each_present_cpu(cpu) {
+        if (cpu_logical_map(cpu) == mpidr) {
+            pr_err("Firmware bug, duplicate CPU MPIDR: 0x%llx in MADT\n",
+                   mpidr);
+            return -EINVAL;
+        }
+    }
+
+skip_mpidr_check:
+    enabled_cpus++;
+
+    /* allocate a logical cpu id for the new comer */
+    if (cpu_logical_map(0) == mpidr) {
+        /*
+         * boot_cpu_init() already hold bit 0 in cpu_present_mask
+         * for BSP, no need to allocate again.
+         */
+        cpu = 0;
+    } else {
+        cpu = cpumask_next_zero(-1, cpu_present_mask);
+    }
+
+    /* map the logical cpu id to cpu MPIDR */
+    cpu_logical_map(cpu) = mpidr;
+
+    set_cpu_possible(cpu, true);

IMO it better to keep all these updates to cpumasks contained in the
smp.c as I had mentioned before. I think you can refactor smp_init_cpus
to achieve that.

Could you give me more hints? smp_init_cpus() use the CPU node in device
tree to map cpu, but in ACPI, they are table entries, if you can give me
more hints about how to refactor it, I will appreciate a lot.

quoted

+    set_cpu_present(cpu, true);

This is totally wrong ? What would you do if the cpu failed to
initialize ? I don't see that handled.

quoted

+
+    return cpu;
+}
+
+static int __init
+acpi_parse_gic_cpu_interface(struct acpi_subtable_header *header,
+                const unsigned long end)
+{
+    struct acpi_madt_generic_interrupt *processor;
+
+    processor = (struct acpi_madt_generic_interrupt *)header;
+
+    if (BAD_MADT_ENTRY(processor, end))
+        return -EINVAL;
+
+    acpi_table_print_madt_entry(header);
+
+    acpi_register_gic_cpu_interface(processor->arm_mpidr,
+        processor->flags & ACPI_MADT_ENABLED);
+
+    return 0;
+}
+
+/*
+ * Parse GIC cpu interface related entries in MADT
+ * returns 0 on success, < 0 on error
+ */
+static int __init acpi_parse_madt_gic_cpu_interface_entries(void)
+{
+    int count;
+
+    /*
+     * do a partial walk of MADT to determine how many CPUs
+     * we have including disabled CPUs, and get information
+     * we need for SMP init
+     */
+    count = acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT,
+            acpi_parse_gic_cpu_interface, MAX_GIC_CPU_INTERFACE);
+
+    if (!count) {
+        pr_err("No GIC CPU interface entries present\n");
+        return -ENODEV;
+    } else if (count < 0) {
+        pr_err("Error parsing GIC CPU interface entry\n");
+        return count;
+    }
+
+    /* Make boot-up look pretty */
+    pr_info("%d CPUs enabled, %d CPUs total\n", enabled_cpus, total_cpus);

Ideally just setup cpu_logical_map in acpi_parse_gic_cpu_interface and
setup cpumasks in smp_init_cpus.

quoted

+
+    return 0;
+}
+
  static int __init acpi_parse_fadt(struct acpi_table_header *table)
  {
      struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;

@@ -99,8 +220,12 @@ int __init acpi_boot_init(void)
          return -ENODEV;

      err = acpi_table_parse(ACPI_SIG_FADT, acpi_parse_fadt);
-    if (err)
-        pr_err("Can't find FADT\n");
+    if (err) {
+        pr_err("Can't find FADT or error happened during parsing FADT\n");
+        return err;
+    }
+
+    err = acpi_parse_madt_gic_cpu_interface_entries();

      return err;
  }

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 40f38f4..8f1d37c 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c

@@ -36,6 +36,7 @@
  #include <linux/completion.h>
  #include <linux/of.h>
  #include <linux/irq_work.h>
+#include <linux/acpi.h>

  #include <asm/atomic.h>
  #include <asm/cacheflush.h>

@@ -458,7 +459,14 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
          if (err)
              continue;

-        set_cpu_present(cpu, true);
+        /*
+         * In ACPI mode, cpu_present_map was initialised when
+         * MADT table was parsed which before this function
+         * is called.
+         */
+        if (acpi_disabled)
+            set_cpu_present(cpu, true);
+

This is the right place to set the cpu present based on the return value
of cpu_prepare.

Yes, as I replied in previous email, I will update the patch and consider
CPU hotplug in the future.

Thanks
Hanjun