linux-kernel - Re: [PATCH v2 03/10] PCI/LUO: Forward prepare()/freeze()/cancel() callbacks to driver

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Message-ID: <2025100317-backroom-upside-c788@gregkh>
Date: Fri, 3 Oct 2025 14:26:51 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Chris Li <chrisl@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>, Len Brown <lenb@...nel.org>,
	Pasha Tatashin <pasha.tatashin@...een.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org, David Matlack <dmatlack@...gle.com>,
	Pasha Tatashin <tatashin@...gle.com>,
	Jason Miu <jasonmiu@...gle.com>, Vipin Sharma <vipinsh@...gle.com>,
	Saeed Mahameed <saeedm@...dia.com>,
	Adithya Jayachandran <ajayachandra@...dia.com>,
	Parav Pandit <parav@...dia.com>, William Tu <witu@...dia.com>,
	Mike Rapoport <rppt@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>,
	Leon Romanovsky <leon@...nel.org>
Subject: Re: [PATCH v2 03/10] PCI/LUO: Forward prepare()/freeze()/cancel()
 callbacks to driver

On Fri, Oct 03, 2025 at 12:26:01AM -0700, Chris Li wrote:
> On Thu, Oct 2, 2025 at 11:19 PM Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >
> > On Thu, Oct 02, 2025 at 01:38:56PM -0700, Chris Li wrote:
> > > On Tue, Sep 30, 2025 at 8:30 AM Greg Kroah-Hartman
> > > <gregkh@...uxfoundation.org> wrote:
> > > >
> > > > On Tue, Sep 16, 2025 at 12:45:11AM -0700, Chris Li wrote:
> > > > >  include/linux/dev_liveupdate.h |  23 +++++
> > > > >  include/linux/device/driver.h  |   6 ++
> > > >
> > > > Driver core changes under the guise of only PCI changes?  Please no.
> > >
> > > There is a reason why I use the device struct rather than the pci_dev
> > > struct even though liveupdate currently only works with PCI devices.
> > > It comes down to the fact that the pci_bus and pci_host_bridge are not
> > > pci_dev struct. We need something that is common across all those
> > > three types of PCI related struct I care about(pci_dev, pci_bus,
> > > pci_host_bridge). The device struct is just common around those. I can
> > > move the dev_liveupdate struct into pci_bus, pci_host_bridge and
> > > pci_dev independently. That will be more contained inside PCI, not
> > > touching the device struct. The patch would be bigger because the data
> > > structure is spread into different structs. Do you have a preference
> > > which way to go?
> >
> > If you only are caring about one single driver, don't mess with a
> > subsystem or the driver core, just change the driver.  My objection here
> 
> It is more than just one driver, we have vfio-pci, idpf, pci-pf-stub
> and possible nvme driver.

Why is nvme considered a "GPU" that needs context saved?

> The change needs to happen in the PCI enumeration and probing as well,
> that is outside of the driver code.

So all just PCI drivers?  Then keep this in PCI-only please, and don't
touch the driver core.

> > was that you were claiming it was a PCI change, yet it was actually only
> > touching the driver core which means that all devices in the systems for
> 
> In theory all the devices can be liveupdate preserved. But now we only
> support PCI.

Then for now, only focus on PCI.

thanks,

greg k-h