linux-kernel - Re: [RFC PATCH 00/21] VFIO live update support

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Message-ID: <20251018230641.GR3938986@ziepe.ca>
Date: Sat, 18 Oct 2025 20:06:41 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Vipin Sharma <vipinsh@...gle.com>
Cc: bhelgaas@...gle.com, alex.williamson@...hat.com,
	pasha.tatashin@...een.com, dmatlack@...gle.com, graf@...zon.com,
	pratyush@...nel.org, gregkh@...uxfoundation.org, chrisl@...nel.org,
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	saeedm@...dia.com, kevin.tian@...el.com, jrhilke@...gle.com,
	david@...hat.com, jgowans@...zon.com, dwmw2@...radead.org,
	epetron@...zon.de, junaids@...gle.com, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [RFC PATCH 00/21] VFIO live update support

On Sat, Oct 18, 2025 at 03:53:09PM -0700, Vipin Sharma wrote:
> On 2025-10-18 14:21:30, Jason Gunthorpe wrote:
> > On Fri, Oct 17, 2025 at 05:06:52PM -0700, Vipin Sharma wrote:
> > > 2. Integration with IOMMUFD and PCI series for complete workflow where a
> > >    device continues a DMA while undergoing through live update.
> > 
> > It is a bit confusing, this series has PCI components so how does it
> > relate the PCI series? Is this self contained for at least limited PCI
> > topologies?
> 
> This series has very minimal PCI support. For example, it is skipping
> DMA disable on the VFIO PCI device during kexec reboot and saving initial PCI
> state during first open (bind) of the device.
> 
> We do need proper PCI support, few examples:
> 
> - Not disabling DMA bit on bridges upstream of the leaf VFIO PCI device node.

So limited to topology without bridges

> - Not writing to PCI config during device enumeration.

I think this should be included here

> - Not autobinding devices to their default driver. My testing works on
>   devices which don't have driver bulit in the kernel so there is no
>   probing by other drivers.

Good enough for now, easy to not build in such drivers.

> - PCI enable and disable calls support.

?? Shouldn't vfio restore skip calling pci enable? Seems like there
should be some solution here.

Jason