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Date:   Fri, 14 May 2021 23:24:53 -0700
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Subject: Re: [PATCH v2 7/9] x86/irq: WARN_ONCE() if irq_move_cleanup is called on a pending interrupt
To:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>
CC:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
From:   "H. Peter Anvin" <hpa@zytor.com>
Message-ID: <09189009-FB0A-4DFA-917E-F447EB21798D@zytor.com>
Precedence: bulk

Ugh=2E=2E=2E I could swear I had fixed the patch description=2E

On May 14, 2021 6:43:59 PM PDT, "H=2E Peter Anvin" <hpa@zytor=2Ecom> wrote=
:
>From: "H=2E Peter Anvin (Intel)" <hpa@zytor=2Ecom>
>
>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=2E This should make it possible to move it to the "normal"
>system IRQ vector range=2E This should probably be a three-step process:
>
>1=2E Introduce this WARN_ONCE() on this event ever occurring=2E
>2=2E Move the IRQ_MOVE_CLEANUP_VECTOR to the sysvec range=2E
>3=2E Remove the self-IPI hack=2E
>
>This implements step 1=2E
>
>Suggested-by: Thomas Gleixner <tglx@linutronix=2Ede>
>Signed-off-by: H=2E Peter Anvin (Intel) <hpa@zytor=2Ecom>
>---
> arch/x86/kernel/apic/vector=2Ec | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/arch/x86/kernel/apic/vector=2Ec
>b/arch/x86/kernel/apic/vector=2Ec
>index 6dbdc7c22bb7=2E=2E7ba2982a3585 100644
>--- a/arch/x86/kernel/apic/vector=2Ec
>+++ b/arch/x86/kernel/apic/vector=2Ec
>@@ -939,9 +939,14 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_irq_move_cleanup)
> 		 * to this CPU=2E IRQ_MOVE_CLEANUP_VECTOR is the lowest
> 		 * priority external vector, so on return from this
> 		 * interrupt the device interrupt will happen first=2E
>+		 *
>+		 * *** This should never happen with the current IRQ
>+		 * cleanup code, so WARN_ONCE() for now, and
>+		 * eventually get rid of this hack=2E
> 		 */
> 		irr =3D 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;
> 		}

--=20
Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E