Patch "nvme: apply DELAY_BEFORE_CHK_RDY quirk at probe time too" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    nvme: apply DELAY_BEFORE_CHK_RDY quirk at probe time too

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nvme-apply-delay_before_chk_rdy-quirk-at-probe-time-too.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From b5a10c5f7532b7473776da87e67f8301bbc32693 Mon Sep 17 00:00:00 2001
From: "Guilherme G. Piccoli" <gpiccoli@linux.vnet.ibm.com>
Date: Wed, 28 Dec 2016 22:13:15 -0200
Subject: nvme: apply DELAY_BEFORE_CHK_RDY quirk at probe time too

From: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>

commit b5a10c5f7532b7473776da87e67f8301bbc32693 upstream.

Commit 54adc01055b7 ("nvme/quirk: Add a delay before checking for adapter
readiness") introduced a quirk to adapters that cannot read the bit
NVME_CSTS_RDY right after register NVME_REG_CC is set; these adapters
need a delay or else the action of reading the bit NVME_CSTS_RDY could
somehow corrupt adapter's registers state and it never recovers.

When this quirk was added, we checked ctrl->tagset in order to avoid
quirking in probe time, supposing we would never require such delay
during probe. Well, it was too optimistic; we in fact need this quirk
at probe time in some cases, like after a kexec.

In some experiments, after abnormal shutdown of machine (aka power cord
unplug), we booted into our bootloader in Power, which is a Linux kernel,
and kexec'ed into another distro. If this kexec is too quick, we end up
reaching the probe of NVMe adapter in that distro when adapter is in
bad state (not fully initialized on our bootloader). What happens next
is that nvme_wait_ready() is unable to complete, except if the quirk is
enabled.

So, this patch removes the original ctrl->tagset verification in order
to enable the quirk even on probe time.

Fixes: 54adc01055b7 ("nvme/quirk: Add a delay before checking for adapter readiness")
Reported-by: Andrew Byrne <byrneadw@ie.ibm.com>
Reported-by: Jaime A. H. Gomez <jahgomez@mx1.ibm.com>
Reported-by: Zachary D. Myers <zdmyers@us.ibm.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Acked-by: Jeffrey Lien <Jeff.Lien@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/nvme/host/core.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1122,12 +1122,7 @@ int nvme_disable_ctrl(struct nvme_ctrl *
 	if (ret)
 		return ret;
 
-	/* Checking for ctrl->tagset is a trick to avoid sleeping on module
-	 * load, since we only need the quirk on reset_controller. Notice
-	 * that the HGST device needs this delay only in firmware activation
-	 * procedure; unfortunately we have no (easy) way to verify this.
-	 */
-	if ((ctrl->quirks & NVME_QUIRK_DELAY_BEFORE_CHK_RDY) && ctrl->tagset)
+	if (ctrl->quirks & NVME_QUIRK_DELAY_BEFORE_CHK_RDY)
 		msleep(NVME_QUIRK_DELAY_AMOUNT);
 
 	return nvme_wait_ready(ctrl, cap, false);


Patches currently in stable-queue which might be from gpiccoli@linux.vnet.ibm.com are

queue-4.9/nvme-apply-delay_before_chk_rdy-quirk-at-probe-time-too.patch