linux-kernel - Re: [PATCH v2] PCI: Disable Samsung SM951/PM951 NVMe before FLR

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Date:   Thu, 1 Jul 2021 20:59:49 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Robert Straw <drbawb@...alsyntax.com>, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        alex.williamson@...hat.com
Subject: Re: [PATCH v2] PCI: Disable Samsung SM951/PM951 NVMe before FLR

On Thu, Jul 01, 2021 at 02:38:56PM -0500, Bjorn Helgaas wrote:
> On Fri, Apr 30, 2021 at 06:01:19PM -0500, Robert Straw wrote:
> > The SM951/PM951, when used in conjunction with the vfio-pci driver and
> > passed to a KVM guest, can exhibit the fatal state addressed by the
> > existing `nvme_disable_and_flr` quirk. If the guest cleanly shuts down
> > the SSD, and vfio-pci attempts an FLR to the device while it is in this
> > state, the nvme driver will fail when it attempts to bind to the device
> > after the FLR due to the frozen config area, e.g:
> > 
> >   nvme nvme2: frozen state error detected, reset controller
> >   nvme nvme2: Removing after probe failure status: -12
> > 
> > By including this older model (Samsung 950 PRO) of the controller in the
> > existing quirk: the device is able to be cleanly reset after being used
> > by a KVM guest.
> > 
> > Signed-off-by: Robert Straw <drbawb@...alsyntax.com>
> 
> Applied to pci/virtualization for v5.14, thanks!

FYI, I really do not like the idea of the PCIe core messing with NVMe
registers like this.