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Date:   Mon, 19 Jul 2021 11:44:14 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     John Garry <john.garry@huawei.com>
Cc:     Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Christoph Hellwig <hch@lst.de>, linux-block@vger.kernel.org,
        linux-nvme@lists.infradead.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        Daniel Wagner <dwagner@suse.de>,
        Wen Xiong <wenxiong@us.ibm.com>,
        Hannes Reinecke <hare@suse.de>, Keith Busch <kbusch@kernel.org>
Subject: Re: [PATCH V4 1/3] driver core: mark device as irq affinity
 managed if any irq is managed
Message-ID: <20210719094414.GC431@lst.de>
References: <20210715120844.636968-1-ming.lei@redhat.com> <20210715120844.636968-2-ming.lei@redhat.com> <5e534fdc-909e-39b2-521d-31f643a10558@huawei.com>
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On Mon, Jul 19, 2021 at 08:51:22AM +0100, John Garry wrote:
>> Address this issue by adding one field of .irq_affinity_managed into
>> 'struct device'.
>>
>> Suggested-by: Christoph Hellwig <hch@lst.de>
>> Signed-off-by: Ming Lei <ming.lei@redhat.com>
>
> Did you consider that for PCI device we effectively have this info already:
>
> bool dev_has_managed_msi_irq(struct device *dev)
> {
> 	struct msi_desc *desc;
>
> 	list_for_each_entry(desc, dev_to_msi_list(dev), list) {
> 		if (desc->affinity && desc->affinity->is_managed)
> 			return true;
> 	}
>
> 	return false;

Just walking the list seems fine to me given that this is not a
performance criticial path.  But what are the locking implications?

Also does the above imply this won't work for your platform MSI case?