The following commit has been merged into the x86/entry branch of tip: Commit-ID: d244d0e195bc12964bcf3b8eef45e715a7f203b0 Gitweb: https://git.kernel.org/tip/d244d0e195bc12964bcf3b8eef45e715a7f203b0 Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Tue, 25 Feb 2020 22:36:41 +01:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Thu, 27 Feb 2020 14:48:40 +01:00 x86/traps: Document do_spurious_interrupt_bug() Add a comment which explains why this empty handler for a reserved vector exists. Requested-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx> Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx> Reviewed-by: Andy Lutomirski <luto@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20200225220216.624165786@xxxxxxxxxxxxx --- arch/x86/kernel/traps.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 474b8cb..7ffb6f4 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -862,6 +862,25 @@ do_simd_coprocessor_error(struct pt_regs *regs, long error_code) dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code) { + /* + * This addresses a Pentium Pro Erratum: + * + * PROBLEM: If the APIC subsystem is configured in mixed mode with + * Virtual Wire mode implemented through the local APIC, an + * interrupt vector of 0Fh (Intel reserved encoding) may be + * generated by the local APIC (Int 15). This vector may be + * generated upon receipt of a spurious interrupt (an interrupt + * which is removed before the system receives the INTA sequence) + * instead of the programmed 8259 spurious interrupt vector. + * + * IMPLICATION: The spurious interrupt vector programmed in the + * 8259 is normally handled by an operating system's spurious + * interrupt handler. However, a vector of 0Fh is unknown to some + * operating systems, which would crash if this erratum occurred. + * + * In theory this could be limited to 32bit, but the handler is not + * hurting and who knows which other CPUs suffer from this. + */ } dotraplinkage void