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Date:   Tue, 6 Jul 2021 07:42:03 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-scsi@vger.kernel.org, Sagi Grimberg <sagi@grimberg.me>,
        Daniel Wagner <dwagner@suse.de>,
        Wen Xiong <wenxiong@us.ibm.com>,
        John Garry <john.garry@huawei.com>,
        Hannes Reinecke <hare@suse.de>,
        Keith Busch <kbusch@kernel.org>,
        Damien Le Moal <damien.lemoal@wdc.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        virtualization@lists.linux-foundation.org,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH V2 5/6] virtio: add one field into virtio_device for
 recording if device uses managed irq
Message-ID: <20210706054203.GC17027@lst.de>
References: <20210702150555.2401722-1-ming.lei@redhat.com> <20210702150555.2401722-6-ming.lei@redhat.com>
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On Fri, Jul 02, 2021 at 11:05:54PM +0800, Ming Lei wrote:
> blk-mq needs to know if the device uses managed irq, so add one field
> to virtio_device for recording if device uses managed irq.
> 
> If the driver use managed irq, this flag has to be set so it can be
> passed to blk-mq.

I don't think all this boilerplate code make a whole lot of sense.
I think we need to record this information deep down in the irq code by
setting a flag in struct device only if pci_alloc_irq_vectors_affinity
atually managed to allocate multiple vectors and the PCI_IRQ_AFFINITY
flag was set.  Then blk-mq can look at that flag, and also check that
more than one queue is in used and work based on that.