linux-kernel - Re: [PATCH v6 05/29] x86/apic/vector: Do not allocate vectors for NMIs

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Message-ID: <87sfpcsf6r.ffs@tglx>
Date:   Sat, 14 May 2022 10:15:24 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     x86@...nel.org, Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <joro@...tes.org>,
        Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Nicholas Piggin <npiggin@...il.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        iommu@...ts.linux-foundation.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 05/29] x86/apic/vector: Do not allocate vectors for NMIs

On Fri, May 13 2022 at 16:45, Ricardo Neri wrote:
> On Fri, May 13, 2022 at 10:50:09PM +0200, Thomas Gleixner wrote:
>> > Also, if lapic_nmi_controller.irq_set_affinity() is NULL, then irq_chips
>> > INTEL-IR, AMD-IR, those using msi_domain_set_affinity() need to check for NULL.
>> > They currently unconditionally call the parent irq_chip's irq_set_affinity().
>> > I see that there is a irq_chip_set_affinity_parent() function. Perhaps it can
>> > be used for this check?
>> 
>> Yes, this lacks obviously a NMI specific set_affinity callback and this
>> can be very trivial and does not have any of the complexity of interrupt
>> affinity assignment. First online CPU in the mask with a fallback to any
>> online CPU.
>
> Why would we need a fallback to any online CPU? Shouldn't it fail if it cannot
> find an online CPU in the mask?

Might as well fail. Let me think about it.

>> I did not claim that this is complete. This was for illustration.
>
> In the reworked patch, may I add a Co-developed-by with your name and your SOB?

Suggested-by is good enough.

Thanks,

        tglx