linux-kernel - Re: [patch V2 04/25] x86/apic: Make apic_pending_intr

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Date:   Fri, 5 Jul 2019 13:37:31 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andrew Cooper <andrew.cooper3@...rix.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Nadav Amit <namit@...are.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Feng Tang <feng.tang@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [patch V2 04/25] x86/apic: Make apic_pending_intr_clear() more robust

On Fri, Jul 5, 2019 at 1:25 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> Andrew,
>
> >
> > These can be addressed by setting TPR to 0x10, which will inhibit
>
> Right, that's easy and obvious.
>

This boots:

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 177aa8ef2afa..5257c40bde6c 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1531,11 +1531,14 @@ static void setup_local_APIC(void)
 #endif

        /*
-        * Set Task Priority to 'accept all'. We never change this
-        * later on.
+        * Set Task Priority to 'accept all except vectors 0-31'.  An APIC
+        * vector in the 16-31 range can be delivered otherwise, but we'll
+        * think it's an exception and terrible things will happen.
+        * We never change this later on.
         */
        value = apic_read(APIC_TASKPRI);
        value &= ~APIC_TPRI_MASK;
+       value |= 0x10;
        apic_write(APIC_TASKPRI, value);

        apic_pending_intr_clear();