From e039dd815941e785203142261397da6ec64d20cc Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 25 Feb 2020 22:36:40 +0100 Subject: x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug() That function returns immediately after conditionally reenabling interrupts which is more than pointless and requires the ASM code to disable interrupts again. Signed-off-by: Thomas Gleixner Reviewed-by: Sean Christopherson Reviewed-by: Alexandre Chartre Reviewed-by: Frederic Weisbecker Reviewed-by: Andy Lutomirski Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20191023123117.871608831@linutronix.de Link: https://lkml.kernel.org/r/20200225220216.518575042@linutronix.de --- arch/x86/kernel/traps.c | 1 - 1 file changed, 1 deletion(-) (limited to 'arch/x86/kernel/traps.c') diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 6ef00eb6fbb9..474b8cb54899 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -862,7 +862,6 @@ do_simd_coprocessor_error(struct pt_regs *regs, long error_code) dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code) { - cond_local_irq_enable(regs); } dotraplinkage void -- cgit v1.2.3 From d244d0e195bc12964bcf3b8eef45e715a7f203b0 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 25 Feb 2020 22:36:41 +0100 Subject: 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 Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Reviewed-by: Alexandre Chartre Reviewed-by: Andy Lutomirski Link: https://lkml.kernel.org/r/20200225220216.624165786@linutronix.de --- arch/x86/kernel/traps.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'arch/x86/kernel/traps.c') diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 474b8cb54899..7ffb6f4dea1c 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 -- cgit v1.2.3 From 65c668f5faebf549db086b7a6841b6f4187b4e4f Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Tue, 25 Feb 2020 22:36:46 +0100 Subject: x86/traps: Stop using ist_enter/exit() in do_int3() #BP is not longer using IST and using ist_enter() and ist_exit() makes it harder to change ist_enter() and ist_exit()'s behavior. Instead open-code the very small amount of required logic. Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Reviewed-by: Alexandre Chartre Reviewed-by: Andy Lutomirski Link: https://lkml.kernel.org/r/20200225220217.150607679@linutronix.de --- arch/x86/kernel/traps.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) (limited to 'arch/x86/kernel/traps.c') diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 7ffb6f4dea1c..c0bc9df8634d 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -572,14 +572,20 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) return; /* - * Use ist_enter despite the fact that we don't use an IST stack. - * We can be called from a kprobe in non-CONTEXT_KERNEL kernel - * mode or even during context tracking state changes. + * Unlike any other non-IST entry, we can be called from a kprobe in + * non-CONTEXT_KERNEL kernel mode or even during context tracking + * state changes. Make sure that we wake up RCU even if we're coming + * from kernel code. * - * This means that we can't schedule. That's okay. + * This means that we can't schedule even if we came from a + * preemptible kernel context. That's okay. */ - ist_enter(regs); + if (!user_mode(regs)) { + rcu_nmi_enter(); + preempt_disable(); + } RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); + #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP, SIGTRAP) == NOTIFY_STOP) @@ -600,7 +606,10 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) cond_local_irq_disable(regs); exit: - ist_exit(regs); + if (!user_mode(regs)) { + preempt_enable_no_resched(); + rcu_nmi_exit(); + } } NOKPROBE_SYMBOL(do_int3); -- cgit v1.2.3