linux-kernel - Re: [PATCH] nvme-pci: Shutdown when removing dead controller

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Message-ID: <CAKcoMVBjzM6dq33DaTYBK6U32U3NQaR5mf6ppGr6iTKRuZ2KNg@mail.gmail.com>
Date:   Sat, 5 Oct 2019 17:58:52 -0400
From:   Tyler Ramer <tyaramer@...il.com>
To:     "Singh, Balbir" <sblbir@...zon.com>
Cc:     "kbusch@...nel.org" <kbusch@...nel.org>, "hch@....de" <hch@....de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "axboe@...com" <axboe@...com>,
        "sagi@...mberg.me" <sagi@...mberg.me>
Subject: Re: [PATCH] nvme-pci: Shutdown when removing dead controller

> What is the bad CSTS bit? CSTS.RDY?

The reset will be triggered by the result of nvme_should_reset():

1196 static bool nvme_should_reset(struct nvme_dev *dev, u32 csts)
1197 {
1198
1199 ⇥       /* If true, indicates loss of adapter communication, possibly by a
1200 ⇥        * NVMe Subsystem reset.
1201 ⇥        */
1202 ⇥       bool nssro = dev->subsystem && (csts & NVME_CSTS_NSSRO);

This csts value is set in nvme_timeout:

1240 static enum blk_eh_timer_return nvme_timeout(struct request *req,
bool reserved)
1241 {
...
1247 ⇥       u32 csts = readl(dev->bar + NVME_REG_CSTS);
...
1256 ⇥       /*
1257 ⇥        * Reset immediately if the controller is failed
1258 ⇥        */
1259 ⇥       if (nvme_should_reset(dev, csts)) {
1260 ⇥       ⇥       nvme_warn_reset(dev, csts);
1261 ⇥       ⇥       nvme_dev_disable(dev, false);
1262 ⇥       ⇥       nvme_reset_ctrl(&dev->ctrl);


Again, here's the message printed by nvme_warn_reset:

Aug 26 15:01:27 testhost kernel: nvme nvme4: controller is down; will
reset: CSTS=0x3, PCI_STATUS=0x10

>From  include/linux/nvme.h:
 105 ⇥       NVME_REG_CSTS⇥  = 0x001c,⇥      /* Controller Status */

- Tyler