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Re: [PATCH] x86/ioapic: sanitize IO-APIC pins before enabling the local APIC
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 17 Jul 2023 08:40:05 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 17 Jul 2023 06:40:24 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 14.07.2023 18:05, Roger Pau Monné wrote:
> On Thu, Jul 13, 2023 at 02:18:29PM +0200, Jan Beulich wrote:
>> On 13.07.2023 13:29, Roger Pau Monné wrote:
>>> So to recap, I think we are in agreement that calling enable_IO_APIC()
>>> just ahead of the call to setup_local_APIC() is the preferred
>>> solution?
>>
>> Well, yes and no. My preferred course of action for the issue at hand
>> would be to convert RTE 0 to ExtInt (under the mentioned set of
>> conditions). I agree though that we also want to move the masking of
>> RTEs, and for that I further agree with the placement mentioned above.
>
> So I hacked up a change to set pin 0 to ExtINT mode (and avoid doing
> the masking early), and I got:
>
> (XEN) spurious 8259A interrupt: IRQ7.
>
> This was a single interrupt, but still I think the masking is the
> critical part to get backported.
One way to look at it, yes. My perspective is different though: If
there truly is a (spurious or not) IRQ at the 8259, then it needs
dealing with sooner or later (in the process of booting). Aiui if
we masked pin 0 initially and then later unmasked it (after
switching to ExtInt, if not set so by firmware), we'd still see a
spurious IRQ7.
Jan
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