linux-kernel - Re: [PATCH 5/5] hisi_acc_vfio_pci: bugfix live migration function without VF device driver

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Message-ID: <20241209135119.GB1888283@ziepe.ca>
Date: Mon, 9 Dec 2024 09:51:19 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Longfang Liu <liulongfang@...wei.com>
Cc: alex.williamson@...hat.com, shameerali.kolothum.thodi@...wei.com,
	jonathan.cameron@...wei.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxarm@...neuler.org
Subject: Re: [PATCH 5/5] hisi_acc_vfio_pci: bugfix live migration function
 without VF device driver

On Fri, Dec 06, 2024 at 05:33:12PM +0800, Longfang Liu wrote:
> If the driver of the VF device is not loaded in the Guest OS,
> then perform device data migration. The migrated data address will
> be NULL.
> The live migration recovery operation on the destination side will
> access a null address value, which will cause access errors.
> 
> Therefore, live migration of VMs without added VF device drivers
> does not require device data migration.
> In addition, when the queue address data obtained by the destination
> is empty, device queue recovery processing will not be performed.

This seems very strange, why can't you migrate over the null DMA addr?
Shouldn't this be fixed on the receiving side?

Jason