linux-kernel - Re: [PATCH v2 7/9] x86/irq: WARN_ONCE() if irq_move

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Date:   Fri, 14 May 2021 23:24:53 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/9] x86/irq: WARN_ONCE() if irq_move_cleanup is called on a pending interrupt

Ugh... I could swear I had fixed the patch description.

On May 14, 2021 6:43:59 PM PDT, "H. Peter Anvin" <hpa@...or.com> wrote:
>From: "H. Peter Anvin (Intel)" <hpa@...or.com>
>
>The current IRQ vector allocation code should be "clean" and never
>issue a IRQ_MOVE_CLEANUP_VECTOR IPI for an interrupt that could still
>be pending. This should make it possible to move it to the "normal"
>system IRQ vector range. This should probably be a three-step process:
>
>1. Introduce this WARN_ONCE() on this event ever occurring.
>2. Move the IRQ_MOVE_CLEANUP_VECTOR to the sysvec range.
>3. Remove the self-IPI hack.
>
>This implements step 1.
>
>Suggested-by: Thomas Gleixner <tglx@...utronix.de>
>Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
>---
> arch/x86/kernel/apic/vector.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/arch/x86/kernel/apic/vector.c
>b/arch/x86/kernel/apic/vector.c
>index 6dbdc7c22bb7..7ba2982a3585 100644
>--- a/arch/x86/kernel/apic/vector.c
>+++ b/arch/x86/kernel/apic/vector.c
>@@ -939,9 +939,14 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_irq_move_cleanup)
> 		 * to this CPU. IRQ_MOVE_CLEANUP_VECTOR is the lowest
> 		 * priority external vector, so on return from this
> 		 * interrupt the device interrupt will happen first.
>+		 *
>+		 * *** This should never happen with the current IRQ
>+		 * cleanup code, so WARN_ONCE() for now, and
>+		 * eventually get rid of this hack.
> 		 */
> 		irr = apic_read(APIC_IRR + (vector / 32 * 0x10));
> 		if (irr & (1U << (vector % 32))) {
>+			WARN_ONCE(1, "irq_move_cleanup called on still pending
>interrupt\n");
> 			apic->send_IPI_self(IRQ_MOVE_CLEANUP_VECTOR);
> 			continue;
> 		}

-- 
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