linux-kernel - Re: [PATCH] xen: Allow platform PCI interrupt to be shared

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Message-ID: <1834b425-2d77-a0c3-e2a9-5c1fc9de750d@suse.com>
Date:   Fri, 20 Jan 2023 08:20:04 +0100
From:   Juergen Gross <jgross@...e.com>
To:     David Woodhouse <dwmw2@...radead.org>
Cc:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel <xen-devel@...ts.xenproject.org>,
        linux-kernel@...r.kernel.org, Paul Durrant <paul@....org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] xen: Allow platform PCI interrupt to be shared

On 18.01.23 13:22, David Woodhouse wrote:
> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> When we don't use the per-CPU vector callback, we ask Xen to deliver event
> channel interrupts as INTx on the PCI platform device. As such, it can be
> shared with INTx on other PCI devices.
> 
> Set IRQF_SHARED, and make it return IRQ_HANDLED or IRQ_NONE according to
> whether the evtchn_upcall_pending flag was actually set. Now I can share
> the interrupt:
> 
>   11:         82          0   IO-APIC  11-fasteoi   xen-platform-pci, ens4
> 
> Drop the IRQF_TRIGGER_RISING. It has no effect when the IRQ is shared,
> and besides, the only effect it was having even beforehand was to trigger
> a debug message in both I/OAPIC and legacy PIC cases:
> 
> [    0.915441] genirq: No set_type function for IRQ 11 (IO-APIC)
> [    0.951939] genirq: No set_type function for IRQ 11 (XT-PIC)
> 
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>

Reviewed-by: Juergen Gross <jgross@...e.com>

> ---
> What does xen_evtchn_do_upcall() exist for? Can we delete it? I don't
> see it being called anywhere.

It can be deleted.


Juergen

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