[PATCH v2 23/26] x86, ioapic: Find usable ioapic id for 64bit.

[Yinghai Lu]

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

Signed-off-by: Yinghai Lu <ying...@kernel.org>
Cc: Joerg Roedel <j...@8bytes.org>
Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Cc: Sebastian Andrzej Siewior <sebast...@breakpoint.cc>
---
 arch/x86/kernel/apic/io_apic.c |   41 +++++++++++++++++++++++++++++++++-------
 1 file changed, 34 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index d4c68d9..42f273b 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3663,27 +3663,54 @@ 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 (i = 0; i < nr_ioapics; i++) {
+       for (i = 0; i < nr_ioapics; i++)
                __set_bit(mpc_ioapic_id(i), used);
-       }
        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
 
@@ -3964,7 +3991,7 @@ int __mp_register_ioapic(int id, u32 address, u32 
gsi_base, bool hotadd)
        if (bad_ioapic_register(idx))
                goto failed;
 
-       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);
 
        /*
-- 
1.7.10.4

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