From 593f4a788e5d09e9f00182561437461b0b564de4 Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Wed, 16 Jul 2008 19:15:30 +0100 Subject: x86: APIC: remove apic_write_around(); use alternatives Use alternatives to select the workaround for the 11AP Pentium erratum for the affected steppings on the fly rather than build time. Remove the X86_GOOD_APIC configuration option and replace all the calls to apic_write_around() with plain apic_write(), protecting accesses to the ESR as appropriate due to the 3AP Pentium erratum. Remove apic_read_around() and all its invocations altogether as not needed. Remove apic_write_atomic() and all its implementing backends. The use of ASM_OUTPUT2() is not strictly needed for input constraints, but I have used it for readability's sake. I had the feeling no one else was brave enough to do it, so I went ahead and here it is. Verified by checking the generated assembly and tested with both a 32-bit and a 64-bit configuration, also with the 11AP "feature" forced on and verified with gdb on /proc/kcore to work as expected (as an 11AP machines are quite hard to get hands on these days). Some script complained about the use of "volatile", but apic_write() needs it for the same reason and is effectively a replacement for writel(), so I have disregarded it. I am not sure what the policy wrt defconfig files is, they are generated and there is risk of a conflict resulting from an unrelated change, so I have left changes to them out. The option will get removed from them at the next run. Some testing with machines other than mine will be needed to avoid some stupid mistake, but despite its volume, the change is not really that intrusive, so I am fairly confident that because it works for me, it will everywhere. Signed-off-by: Maciej W. Rozycki Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/bugs.c | 23 +---------------------- 1 file changed, 1 insertion(+), 22 deletions(-) (limited to 'arch/x86/kernel/cpu/bugs.c') diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 1b1c56bb338..c9b58a806e8 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -131,13 +131,7 @@ static void __init check_popad(void) * (for due to lack of "invlpg" and working WP on a i386) * - In order to run on anything without a TSC, we need to be * compiled for a i486. - * - In order to support the local APIC on a buggy Pentium machine, - * we need to be compiled with CONFIG_X86_GOOD_APIC disabled, - * which happens implicitly if compiled for a Pentium or lower - * (unless an advanced selection of CPU features is used) as an - * otherwise config implies a properly working local APIC without - * the need to do extra reads from the APIC. -*/ + */ static void __init check_config(void) { @@ -151,21 +145,6 @@ static void __init check_config(void) if (boot_cpu_data.x86 == 3) panic("Kernel requires i486+ for 'invlpg' and other features"); #endif - -/* - * If we were told we had a good local APIC, check for buggy Pentia, - * i.e. all B steppings and the C2 stepping of P54C when using their - * integrated APIC (see 11AP erratum in "Pentium Processor - * Specification Update"). - */ -#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC) - if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL - && cpu_has_apic - && boot_cpu_data.x86 == 5 - && boot_cpu_data.x86_model == 2 - && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11)) - panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!"); -#endif } -- cgit v1.2.3-18-g5258