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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc:     x86@kernel.org, Tony Luck <tony.luck@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Stephane Eranian <eranian@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Joerg Roedel <joro@8bytes.org>,
        Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Ricardo Neri <ricardo.neri@intel.com>,
        iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 05/29] x86/apic/vector: Do not allocate vectors for NMIs
In-Reply-To: <20220513234542.GC9074@ranerica-svr.sc.intel.com>
References: <20220506000008.30892-1-ricardo.neri-calderon@linux.intel.com>
 <20220506000008.30892-6-ricardo.neri-calderon@linux.intel.com>
 <87zgjufjrf.ffs@tglx> <20220513180320.GA22683@ranerica-svr.sc.intel.com>
 <87v8u9rwce.ffs@tglx> <20220513234542.GC9074@ranerica-svr.sc.intel.com>
Date:   Sat, 14 May 2022 10:15:24 +0200
Message-ID: <87sfpcsf6r.ffs@tglx>
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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