[PATCH v4 23/28] x86, ioapic: Find usable ioapic id for 64bit.

[Yinghai Lu <yinghai@xxxxxxxxxx>]

Checking the id in register, if that is duplicated, will pick one and
update id register.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <sebastian@xxxxxxxxxxxxx>
---
 arch/x86/kernel/apic/io_apic.c | 38 +++++++++++++++++++++++++++++++++-----
 1 file changed, 33 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index a75e9d8..fb9bf06 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3652,19 +3652,22 @@ static int __init io_apic_get_unique_id(int ioapic, int apic_id)
 	return apic_id;
 }
 
-static u8 __init io_apic_unique_id(u8 id)
+static u8 __init io_apic_unique_id(int idx, u8 id)
 {
 	if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) &&
 	    !APIC_XAPIC(apic_version[boot_cpu_physical_apicid]))
-		return io_apic_get_unique_id(nr_ioapics, id);
+		return io_apic_get_unique_id(idx, id);
 	else
 		return id;
 }
 #else
-static u8 __init io_apic_unique_id(u8 id)
+static u8 io_apic_unique_id(int idx, u8 id)
 {
 	int i;
+	u8 new_id;
+	unsigned long flags;
 	DECLARE_BITMAP(used, 256);
+	union IO_APIC_reg_00 reg_00;
 
 	bitmap_zero(used, 256);
 	for_each_ioapic(i)
@@ -3672,7 +3675,32 @@ static u8 __init io_apic_unique_id(u8 id)
 
 	if (!test_bit(id, used))
 		return id;
-	return find_first_zero_bit(used, 256);
+
+	/* check register at first */
+	raw_spin_lock_irqsave(&ioapic_lock, flags);
+	reg_00.raw = io_apic_read(idx, 0);
+	raw_spin_unlock_irqrestore(&ioapic_lock, flags);
+	new_id = reg_00.bits.ID;
+	if (!test_bit(new_id, used)) {
+		apic_printk(APIC_VERBOSE, KERN_INFO
+			"IOAPIC[%d]: Using reg apic_id %d instead of %d\n",
+			 idx, new_id, id);
+		return new_id;
+	}
+
+	new_id = find_first_zero_bit(used, 256);
+	reg_00.bits.ID = new_id;
+	raw_spin_lock_irqsave(&ioapic_lock, flags);
+	io_apic_write(idx, 0, reg_00.raw);
+	reg_00.raw = io_apic_read(idx, 0);
+	raw_spin_unlock_irqrestore(&ioapic_lock, flags);
+
+	/* Sanity check */
+	if (reg_00.bits.ID != new_id)
+		pr_warn("IOAPIC[%d]: Unable to change apic_id to %d!\n",
+			idx, new_id);
+
+	return new_id;
 }
 #endif
 
@@ -3947,7 +3975,7 @@ int __mp_register_ioapic(int id, u32 address, u32 gsi_base, bool hotadd)
 	if (bad_ioapic_register(idx))
 		goto clear_out;
 
-	ioapics[idx].mp_config.apicid = io_apic_unique_id(id);
+	ioapics[idx].mp_config.apicid = io_apic_unique_id(idx, id);
 	ioapics[idx].mp_config.apicver = io_apic_get_version(idx);
 
 	/*
-- 
1.8.1.4

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