From: "Luis R. Rodriguez" <[email protected]> X86_UP_IOAPIC is a way so that 32-bit UP systems can enable X86_IOAPIC. X86_UP_IOAPIC is only as a visible user option if you are on a 32-bit system but have X86_UP_APIC enabled. X86_UP_APIC will be enabled by force if you have PCI_MSI on 32-bit systems now, X86_UP_APIC will now only be user selectable if you didn't have PCI_MSI enabled and are also not on a X86_32_NON_STANDARD system. Bryan's original patch (refactored commit log in commit 38a1dfda) [0] describes that Intel CE, Intel MID and Intel Quark are all 32-bit uniprocessor systems with IO-APICs, the code change however only *re-enabled* UP_IOAPIC as an *option* when PCI_MSI was enabled, but given that:
1) enabling X86_IOAPIC is the real end goal here 2) enabling X86_IOAPIC only increases the kernel only by 12064 bytes (~12 KiB) 3) enabling X86_IOAPIC will in no way slow down your kernel Let's make a compromise for 32-bit systems and always enable X86_IOAPIC when X86_UP_IOAPIC is enabled as 32-bit systems are not in a state of flux and the price for the size is small with no performance impact. Using: export ARCH=i386 make allnoconfig --> Enabling PCI_MSI make localyesconfig With X86_IO_APIC: mcgrof@ergon ~/linux-next (git::master)$ du -b arch/x86/boot/bzImage 734608 arch/x86/boot/bzImage Without X86_IO_APIC: mcgrof@ergon ~/linux-next (git::master)$ du -b arch/x86/boot/bzImage 722544 arch/x86/boot/bzImage [0] https://lkml.org/lkml/2015/1/22/718 Cc: David Rientjes <[email protected]> Cc: Bjorn Helgaas <[email protected]> Cc: Bryan O'Donoghue <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Andy Shevchenko <[email protected]> Cc: Thomas Petazzoni <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Jan Beulich <[email protected]> Cc: Juergen Gross <[email protected]> Cc: [email protected] Cc: [email protected] Signed-off-by: Luis R. Rodriguez <[email protected]> --- arch/x86/Kconfig | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 110f6ae..b17a8ea 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -899,6 +899,7 @@ config X86_UP_APIC bool "Local APIC support on uniprocessors" if !PCI_MSI default PCI_MSI depends on X86_32 && !SMP && !X86_32_NON_STANDARD + select X86_IO_APIC ---help--- A local APIC (Advanced Programmable Interrupt Controller) is an integrated interrupt controller in the CPU. If you have a single-CPU @@ -909,18 +910,6 @@ config X86_UP_APIC performance counters), and the NMI watchdog which detects hard lockups. -config X86_UP_IOAPIC - bool "IO-APIC support on uniprocessors" - depends on X86_UP_APIC - ---help--- - An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an - SMP-capable replacement for PC-style interrupt controllers. Most - SMP systems and many recent uniprocessor systems have one. - - If you have a single-CPU system with an IO-APIC, you can say Y here - to use it. If you say Y here even though your machine doesn't have - an IO-APIC, then the kernel will still run with no slowdown at all. - config X86_LOCAL_APIC def_bool y depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI @@ -928,7 +917,7 @@ config X86_LOCAL_APIC config X86_IO_APIC def_bool y - depends on X86_LOCAL_APIC || X86_UP_IOAPIC + depends on X86_LOCAL_APIC select IRQ_DOMAIN config X86_REROUTE_FOR_BROKEN_BOOT_IRQS -- 2.3.2.209.gd67f9d5.dirty -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
