linux-kernel - NVMe Poll CQ on timeout

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Date:   Thu, 26 Apr 2018 14:59:06 +0000
From:   Bharat Kumar Gogada <bharatku@...inx.com>
To:     "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "keith.busch@...el.com" <keith.busch@...el.com>,
        "hch@....de" <hch@....de>, "axboe@...com" <axboe@...com>
Subject: NVMe Poll CQ on timeout

Hi,

We are testing NVMe cards on ARM64 platform, the card uses legacy interrupts.
Intermittently we are hitting following case in drivers/nvme/host/pci.c
       /*
         * Did we miss an interrupt?
         */
        if (__nvme_poll(nvmeq, req->tag)) {
                dev_warn(dev->ctrl.device,
                         "I/O %d QID %d timeout, completion polled\n",
                         req->tag, nvmeq->qid);
                return BLK_EH_HANDLED;
        }

Can anyone tell when does nvme_timeout gets invoked ?
What does "Did we miss an interrupt mean" ? Does it mean host missing
to service a interrupt raised by EP card ?

Regards,
Bharat