Re: [PULL for-6.1 06/11] hw/nvme: fix controller hot unplugging

[Klaus Jensen]

On Sep  9 09:02, Hannes Reinecke wrote:
> On 7/26/21 9:18 PM, Klaus Jensen wrote:
> > From: Klaus Jensen <k.jensen@samsung.com>
> > 
> > Prior to this patch the nvme-ns devices are always children of the
> > NvmeBus owned by the NvmeCtrl. This causes the namespaces to be
> > unrealized when the parent device is removed. However, when subsystems
> > are involved, this is not what we want since the namespaces may be
> > attached to other controllers as well.
> > 
> > This patch adds an additional NvmeBus on the subsystem device. When
> > nvme-ns devices are realized, if the parent controller device is linked
> > to a subsystem, the parent bus is set to the subsystem one instead. This
> > makes sure that namespaces are kept alive and not unrealized.
> > 
> > Reviewed-by: Hannes Reinecke <hare@suse.de>
> > Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
> > ---
> >   hw/nvme/nvme.h   | 15 ++++++++-------
> >   hw/nvme/ctrl.c   | 14 ++++++--------
> >   hw/nvme/ns.c     | 18 ++++++++++++++++++
> >   hw/nvme/subsys.c |  3 +++
> >   4 files changed, 35 insertions(+), 15 deletions(-)
> > 
> Finally got around to test this; sadly, with mixed results.
> On the good side: controller hotplug works.
> Within qemu monitor I can do:
> 
> device_del <devname>
> device_add <device description>
> 
> and OS reports:
> [   56.564447] pcieport 0000:00:09.0: pciehp: Slot(0-2): Attention button
> pressed
> [   56.564460] pcieport 0000:00:09.0: pciehp: Slot(0-2): Powering off due to
> button press
> [  104.293335] pcieport 0000:00:09.0: pciehp: Slot(0-2): Attention button
> pressed
> [  104.293347] pcieport 0000:00:09.0: pciehp: Slot(0-2) Powering on due to
> button press
> [  104.293540] pcieport 0000:00:09.0: pciehp: Slot(0-2): Card present
> [  104.293544] pcieport 0000:00:09.0: pciehp: Slot(0-2): Link Up
> [  104.428961] pci 0000:03:00.0: [1b36:0010] type 00 class 0x010802
> [  104.429298] pci 0000:03:00.0: reg 0x10: [mem 0x00000000-0x00003fff 64bit]
> [  104.431442] pci 0000:03:00.0: BAR 0: assigned [mem 0xc1200000-0xc1203fff
> 64bit]
> [  104.431580] pcieport 0000:00:09.0: PCI bridge to [bus 03]
> [  104.431604] pcieport 0000:00:09.0:   bridge window [io  0x7000-0x7fff]
> [  104.434815] pcieport 0000:00:09.0:   bridge window [mem
> 0xc1200000-0xc13fffff]
> [  104.436685] pcieport 0000:00:09.0:   bridge window [mem
> 0x804000000-0x805ffffff 64bit pref]
> [  104.441896] nvme nvme2: pci function 0000:03:00.0
> [  104.442151] nvme 0000:03:00.0: enabling device (0000 -> 0002)
> [  104.455821] nvme nvme2: 1/0/0 default/read/poll queues
> 
> So that works.
> But: the namespace is not reconnected.
> 
> # nvme list-ns /dev/nvme2
> 
> draws a blank. So guess some fixup patch is in order...
> 

Hi Hannes,

I see. Ater the device_del/device_add dance, the namespace is there, but it is
not automatically attached.

    # nvme list-ns -a /dev/nvme0
    [   0]:0x2

    # nvme attach-ns /dev/nvme0 -n 2 -c 0
    attach-ns: Success, nsid:2

    # nvme list-ns /dev/nvme0
    [   0]:0x2


I don't *think* the spec says that namespaces *must* be re-attached
automatically? But I would have to check... If it does say that, then this is a
bug of course.

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