From: Thomas Gleixner <tglx@linutronix.de>
To: Vitaly Kuznetsov <vkuznets@redhat.com>, x86@kernel.org
Cc: Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC 1/2] x86/apic: Do not make an exception for PIC_CASCADE_IR when marking legacy irqs in irq_matrix
Date: Wed, 17 Mar 2021 22:18:39 +0100 [thread overview]
Message-ID: <87blbhxyvk.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <87im5py1ty.fsf@nanos.tec.linutronix.de>
On Wed, Mar 17 2021 at 21:14, Thomas Gleixner wrote:
> On Fri, Feb 19 2021 at 12:31, Vitaly Kuznetsov wrote:
> Even without looking at the machine I can tell you what's going on. MP
> config or ACPI has a pin assigned to IRQ 2 which I've not seen before.
> The code there is ignoring IRQ 2 because that's how the original code
> worked as well as it is reserved for the PIC_CASCADE_IRQ which should
> never fire and we actually want to catch an spurious interrupt on it.
>
> So depending on the overall configuration of that system and the
> resulting delivery modes this might be ok, but I'm really nervous about
> doing this wholesale as it might break old machines.
>
> Out of paranoia I'd rather ignore that IO/APIC pin completely if it
> claims to be IRQ2. I assume there is no device connected to it at all,
> right?
Seems at some point we lost the 'ignore cascade IRQ' logic in
IO/APIC. There is still a comment to that effect.
Let me do some archaeology.
Thanks,
tglx
next prev parent reply other threads:[~2021-03-17 21:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-19 11:30 [PATCH RFC 0/2] x86/apic: Avoid cm->allocated going negative in irq_matrix Vitaly Kuznetsov
2021-02-19 11:31 ` [PATCH RFC 1/2] x86/apic: Do not make an exception for PIC_CASCADE_IR when marking legacy irqs " Vitaly Kuznetsov
2021-03-17 20:14 ` Thomas Gleixner
2021-03-17 21:18 ` Thomas Gleixner [this message]
2021-03-17 21:40 ` Thomas Gleixner
2021-03-17 22:52 ` Thomas Gleixner
2021-03-18 8:47 ` Vitaly Kuznetsov
2021-03-18 8:29 ` Vitaly Kuznetsov
2021-03-18 10:10 ` Thomas Gleixner
2021-02-19 11:31 ` [PATCH RFC 2/2] genirq/matrix: WARN_ON_ONCE() when cm->allocated/m->total_allocated go negative Vitaly Kuznetsov
2021-03-17 20:38 ` Thomas Gleixner
2021-03-18 7:58 ` Vitaly Kuznetsov
2021-03-18 19:29 ` Thomas Gleixner
2021-03-19 9:59 ` Vitaly Kuznetsov
2021-03-11 10:19 ` [PATCH RFC 0/2] x86/apic: Avoid cm->allocated going negative in irq_matrix Vitaly Kuznetsov
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