linux-kernel - [Patch v8 10/18] x86, irq: Prefer assigned ID in APIC ID register for x86

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Date:	Sun,  2 Nov 2014 14:04:25 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>, x86@...nel.org,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Grant Likely <grant.likely@...aro.org>,
	Prarit Bhargava <prarit@...hat.com>
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tony Luck <tony.luck@...el.com>,
	Joerg Roedel <joro@...tes.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>,
	Ingo Molnar <mingo@...nel.org>
Subject: [Patch v8 10/18] x86, irq: Prefer assigned ID in APIC ID register for x86_64

From: Yinghai Lu <yinghai@...nel.org>

Perfer the assigned ID in APIC ID register for x86_64 if it's still
available.

Signed-off-by: Yinghai Lu <yinghai@...nel.org>
Cc: Joerg Roedel <joro@...tes.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
---
 arch/x86/kernel/apic/io_apic.c |   35 ++++++++++++++++++++++++++++++-----
 1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index acaee90fc9cc..eaa7ea385600 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3580,26 +3580,51 @@ 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 __init 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)
 		__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 */
+	BUG_ON(reg_00.bits.ID != new_id);
+
+	return new_id;
 }
 #endif
 
@@ -3865,7 +3890,7 @@ void __init mp_register_ioapic(int id, u32 address, u32 gsi_base,
 		return;
 	}
 
-	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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