[RFC Patch V1 3/4] x86, irq, ACPI: implement interface to support ACPI based IOAPIC hot-addition

[Jiang Liu <jiang.liu@linux.intel.com>]

Implement acpi_register_ioapic() and enhance mp_register_ioapic()
to support ACPI based IOAPIC hot-addition.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 arch/x86/kernel/acpi/boot.c    |   18 ++++++++++++++++--
 arch/x86/kernel/apic/io_apic.c |   24 +++++++++++++++++++++---
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index a1b388e88bcb..d807e16f8fec 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -655,8 +655,22 @@ EXPORT_SYMBOL(acpi_unmap_lsapic);
 
 int acpi_register_ioapic(acpi_handle handle, u64 phys_addr, u32 gsi_base)
 {
-	/* TBD */
-	return -EINVAL;
+	int ret = -ENOSYS;
+#ifdef CONFIG_X86_IO_APIC
+	unsigned long long uid;
+	acpi_status status;
+
+	status = acpi_evaluate_integer(handle, METHOD_NAME__UID, NULL, &uid);
+	if (ACPI_FAILURE(status))
+		uid = 0;
+
+	down_write(&acpi_ioapic_rwsem);
+	ret  = mp_register_ioapic((int)uid, phys_addr, gsi_base,
+				  acpi_create_irqdomain, NULL);
+	up_write(&acpi_ioapic_rwsem);
+#endif
+
+	return ret;
 }
 
 EXPORT_SYMBOL(acpi_register_ioapic);
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index f70fa239f34b..4bddff760ff4 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3802,7 +3802,13 @@ static int bad_ioapic_register(int idx)
 
 static int find_free_ioapic_entry(void)
 {
-	return nr_ioapics;
+	int idx;
+
+	for (idx = 0; idx < MAX_IO_APICS; idx++)
+		if (ioapics[idx].nr_registers == 0)
+			return idx;
+
+	return MAX_IO_APICS;
 }
 
 int mp_register_ioapic(int id, u32 address, u32 gsi_base,
@@ -3818,8 +3824,15 @@ int mp_register_ioapic(int id, u32 address, u32 gsi_base,
 	}
 	for_each_ioapic(ioapic)
 		if (ioapics[ioapic].mp_config.apicaddr == address) {
-			pr_warn("address 0x%x conflicts with IOAPIC%d\n",
-				address, ioapic);
+			/*
+			 * IOAPIC unit may also be visible in PCI scope.
+			 * When ioapic PCI driver's probe() is called,
+			 * the IOAPIC unit may have already been initialized
+			 * at boot time.
+			 */
+			if (!ioapic_initialized)
+				pr_warn("address 0x%x conflicts with IOAPIC%d\n",
+					address, ioapic);
 			return -EEXIST;
 		}
 
@@ -3875,6 +3888,11 @@ int mp_register_ioapic(int id, u32 address, u32 gsi_base,
 	if (nr_ioapics <= idx)
 		nr_ioapics = idx + 1;
 
+	if (ioapic_initialized && ioapic_create_irqdomain(idx)) {
+		clear_fixmap(FIX_IO_APIC_BASE_0 + idx);
+		return -ENOMEM;
+	}
+
 	/* Set nr_registers to mark entry present */
 	ioapics[idx].nr_registers = entries;
 
-- 
1.7.10.4