linux-kernel - [RFC -tip] x86,apic -- reduce disable

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Message-ID: <20090705162044.GC4791@lenovo>
Date:	Sun, 5 Jul 2009 20:20:44 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	Ingo Molnar <mingo@...e.hu>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <yinghai@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [RFC -tip] x86,apic -- reduce disable_apic usage

Here is an attempt to bring more consistency for apic
presence check. I hope I covered all the code flows.
Though it's RFC. Please review and test if possible.

	-- Cyrill
---
Instead of messing with (cpu_has_apic|disable_apic)
to check if we have apic functional, better to distinguish
them by logical kind. cpu_has_apic -- to check if we may
use apic functionality, disable_apic -- to note that
apic was disabled via command line.

Other interesting (and a side one) issue I guess is that
X86_FEATURE_APIC feature bit is always cleared if apic
disabled via command line but not the reverse.

Eventually this allow us to save a few lines of code.

Also:

1) No need to clear bit twice in APIC_init_uniprocessor.
   cpu_has_apic check for boot_cpu_data bit anyway.
2) Don't check for disable_apic in print_all_ICs. It's
   already set. Always.
3) Don't set disable_apic if there is no MPS support built in
   with acpi enabled. Even having SMP built kernel we're
   protected by acpi_lapic check in smp_sanity_check.
   At least we should be.

Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
---
 arch/x86/kernel/apic/apic.c    |    3 +--
 arch/x86/kernel/apic/io_apic.c |    6 +++---
 arch/x86/kernel/setup.c        |    6 +-----
 3 files changed, 5 insertions(+), 10 deletions(-)

Index: linux-2.6.git/arch/x86/kernel/apic/apic.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/apic/apic.c
+++ linux-2.6.git/arch/x86/kernel/apic/apic.c
@@ -1173,7 +1173,7 @@ void __cpuinit setup_local_APIC(void)
 	unsigned int value;
 	int i, j;
 
-	if (disable_apic) {
+	if (!cpu_has_apic) {
 		arch_disable_smp_support();
 		return;
 	}
@@ -1651,7 +1651,6 @@ int __init APIC_init_uniprocessor(void)
 	    APIC_INTEGRATED(apic_version[boot_cpu_physical_apicid])) {
 		pr_err("BIOS bug, local APIC 0x%x not detected!...\n",
 			boot_cpu_physical_apicid);
-		clear_cpu_cap(&boot_cpu_data, X86_FEATURE_APIC);
 		return -1;
 	}
 #endif
Index: linux-2.6.git/arch/x86/kernel/apic/io_apic.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/apic/io_apic.c
+++ linux-2.6.git/arch/x86/kernel/apic/io_apic.c
@@ -1884,7 +1884,7 @@ __apicdebuginit(int) print_all_ICs(void)
 	print_PIC();
 
 	/* don't print out if apic is not there */
-	if (!cpu_has_apic || disable_apic)
+	if (!cpu_has_apic)
 		return 0;
 
 	print_all_local_APICs();
@@ -3261,7 +3261,7 @@ static int msi_compose_msg(struct pci_de
 	int err;
 	unsigned dest;
 
-	if (disable_apic)
+	if (!cpu_has_apic)
 		return -ENXIO;
 
 	cfg = irq_cfg(irq);
@@ -3714,7 +3714,7 @@ int arch_setup_ht_irq(unsigned int irq, 
 	struct irq_cfg *cfg;
 	int err;
 
-	if (disable_apic)
+	if (!cpu_has_apic)
 		return -ENXIO;
 
 	cfg = irq_cfg(irq);
Index: linux-2.6.git/arch/x86/kernel/setup.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/setup.c
+++ linux-2.6.git/arch/x86/kernel/setup.c
@@ -795,12 +795,8 @@ void __init setup_arch(char **cmdline_p)
 	/* after early param, so could get panic from serial */
 	reserve_early_setup_data();
 
-	if (acpi_mps_check()) {
-#ifdef CONFIG_X86_LOCAL_APIC
-		disable_apic = 1;
-#endif
+	if (acpi_mps_check())
 		setup_clear_cpu_cap(X86_FEATURE_APIC);
-	}
 
 #ifdef CONFIG_PCI
 	if (pci_early_dump_regs)
--
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