linux-kernel - Re: [PATCH] x86: Re-enable IO-APIC for non-SMP X86

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Date:	Thu, 22 Jan 2015 22:42:26 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Bryan O'Donoghue <pure.logic@...us-software.ie>
cc:	mingo@...hat.com, hpa@...or.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Re-enable IO-APIC for non-SMP X86_32

On Thu, 22 Jan 2015, Bryan O'Donoghue wrote:

> Commit 0dbc6078c0 ('x86, build, pci: Fix PCI_MSI build on !SMP')
> introduced the dependency that X86_UP_APIC should only be visible only when
> PCI_MSI is false.

I think the intention of the patch was to NOT expose the option when
MSI is enabled, so you cannot turn it off, which makes sense.

But that went wrong.....

> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -857,7 +857,7 @@ source "kernel/Kconfig.preempt"
>  
>  config X86_UP_APIC
>  	bool "Local APIC support on uniprocessors"
> -	depends on X86_32 && !SMP && !X86_32_NON_STANDARD && !PCI_MSI
> +	depends on X86_32 && !SMP && !X86_32_NON_STANDARD

So the proper fix is below.

Thanks,

	tglx
---

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ffcc3ca5862a..a0dbc33690f0 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -861,7 +861,7 @@ config UP_LATE_INIT
 
 config X86_UP_APIC
 	bool "Local APIC support on uniprocessors"
-	depends on X86_32 && !SMP && !X86_32_NON_STANDARD && !PCI_MSI
+	depends on X86_32 && !SMP && !X86_32_NON_STANDARD
 	---help---
 	  A local APIC (Advanced Programmable Interrupt Controller) is an
 	  integrated interrupt controller in the CPU. If you have a single-CPU
@@ -872,6 +872,10 @@ config X86_UP_APIC
 	  performance counters), and the NMI watchdog which detects hard
 	  lockups.
 
+config X86_UP_APIC_MSI
+	def_bool y
+	select X86_UP_APIC if X86_32 && !SMP && !X86_32_NON_STANDARD && PCI_MSI
+
 config X86_UP_IOAPIC
 	bool "IO-APIC support on uniprocessors"
 	depends on X86_UP_APIC

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