linux-kernel - Re: [RFC PATCH v4 18/21] x86/apic: Add a parameter for the APIC delivery mode

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Message-ID: <alpine.DEB.2.21.1906190115240.1765@nanos.tec.linutronix.de>
Date:   Wed, 19 Jun 2019 01:15:39 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
cc:     Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...e.de>,
        Ashok Raj <ashok.raj@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        Andi Kleen <andi.kleen@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
        Stephane Eranian <eranian@...gle.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Randy Dunlap <rdunlap@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Ricardo Neri <ricardo.neri@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Jacob Pan <jacob.jun.pan@...el.com>,
        Juergen Gross <jgross@...e.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Wincy Van <fanwenyi0529@...il.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Baoquan He <bhe@...hat.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: Re: [RFC PATCH v4 18/21] x86/apic: Add a parameter for the APIC
 delivery mode

On Tue, 18 Jun 2019, Ricardo Neri wrote:

> On Sun, Jun 16, 2019 at 11:55:03AM +0200, Thomas Gleixner wrote:
> > On Thu, 23 May 2019, Ricardo Neri wrote:
> > >  
> > >  struct irq_cfg {
> > > -	unsigned int		dest_apicid;
> > > -	unsigned int		vector;
> > > +	unsigned int				dest_apicid;
> > > +	unsigned int				vector;
> > > +	enum ioapic_irq_destination_types	delivery_mode;
> > 
> > And how is this related to IOAPIC?
> 
> In my view, IOAPICs can also be programmed with a delivery mode. Mode
> values are the same for MSI interrupts.

> > I know this enum exists already, but in
> > connection with MSI this does not make any sense at all.
> 
> Is the issue here the name of the enumeration?
> 
> > 
> > > +
> > > +		/*
> > > +		 * Initialize the delivery mode of this irq to match the
> > > +		 * default delivery mode of the APIC. This is useful for
> > > +		 * children irq domains which want to take the delivery
> > > +		 * mode from the individual irq configuration rather
> > > +		 * than from the APIC.
> > > +		 */
> > > +		 apicd->hw_irq_cfg.delivery_mode = apic->irq_delivery_mode;
> > 
> > And here it's initialized from apic->irq_delivery_mode, which is an
> > u32. Intuitive and consistent - NOT!
> 
> Yes, this is wrong. Then should the member in the structure above be an
> u32 instead of enum ioapic_irq_destination_types?
> 
> Thanks and BR,
> Ricardo
>