From: John Levon <john.levon@nutanix.com>
To: Hugo Komatsu <hugo.komatsu@nutanix.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"qemu-s390x@nongnu.org" <qemu-s390x@nongnu.org>,
"Alex Williamson" <alex@shazbot.org>,
"Cédric Le Goater" <clg@redhat.com>,
"Cornelia Huck" <cohuck@redhat.com>,
"Eric Farman" <farman@linux.ibm.com>,
"Halil Pasic" <pasic@linux.ibm.com>,
"Jason Herne" <jjherne@linux.ibm.com>,
"Mark Cave-Ayland" <mark.cave-ayland@ilande.co.uk>,
"Matthew Rosato" <mjrosato@linux.ibm.com>,
"Pierrick Bouvier" <pierrick.bouvier@oss.qualcomm.com>,
"Rafael Castillo" <rafael@trfs.me>,
"Thanos Makatos" <thanos.makatos@nutanix.com>,
"Tony Krowiak" <akrowiak@linux.ibm.com>
Subject: Re: [PATCH 6/8] vfio-user: enable DMA logging for dirty page tracking
Date: Tue, 8 Sep 2026 15:52:46 +0100 [thread overview]
Message-ID: <aqAhPpMOoYERK0WM@lent> (raw)
In-Reply-To: <20260903130833.1437632-7-hugo.komatsu@nutanix.com>
On Thu, Sep 03, 2026 at 02:08:49PM +0100, Hugo Komatsu wrote:
> Forward the DMA logging features to the server so QEMU can perform
> device dirty page tracking. START/STOP and the feature probe map onto
> the existing device_feature message path.
>
> REPORT needs bespoke handling: the kernel struct
> vfio_device_feature_dma_logging_report carries the dirty bitmap by
> pointer, whereas over vfio-user the bitmap travels inline after the
> report header. Translate to the wire layout, size argsz to include
> the bitmap, and copy the returned bitmap back into the caller buffer.
>
> The server only tracks dirty pages for ranges it has DMA-mapped. A
> range it cannot translate (e.g. firmware/MMIO regions never mapped to
> the device) cannot have been dirtied by device DMA, so such a report
> is treated as clean rather than failing the migration.
>
> Signed-off-by: Hugo Komatsu <hugo.komatsu@nutanix.com>
Reviewed-by: John Levon <john.levon@nutanix.com>
next prev parent reply other threads:[~2026-09-08 14:53 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-03 13:08 [PATCH 0/8] vfio-user: live migration support Hugo Komatsu
2026-09-03 13:08 ` [PATCH 1/8] vfio-user: add live migration to vfio-user protocol specification Hugo Komatsu
2026-09-08 14:41 ` John Levon
2026-09-03 13:08 ` [PATCH 2/8] docs/vfio-user: clarify data_fd and DMA logging behaviors Hugo Komatsu
2026-09-08 14:42 ` John Levon
2026-09-03 13:08 ` [PATCH 3/8] vfio: route device_feature through io_ops Hugo Komatsu
2026-09-03 15:35 ` Cédric Le Goater
2026-09-03 13:08 ` [PATCH 4/8] vfio: route device_reset " Hugo Komatsu
2026-09-03 15:44 ` Cédric Le Goater
2026-09-03 13:08 ` [PATCH 5/8] vfio: use io_ops abstraction for migration related ioctls Hugo Komatsu
2026-09-08 14:47 ` John Levon
2026-09-03 13:08 ` [PATCH 6/8] vfio-user: enable DMA logging for dirty page tracking Hugo Komatsu
2026-09-08 14:52 ` John Levon [this message]
2026-09-03 13:08 ` [PATCH 7/8] vfio-user: implement mig_data read/write socket operations Hugo Komatsu
2026-09-08 14:55 ` John Levon
2026-09-03 13:08 ` [PATCH 8/8] vfio-user: enable live migration for pci devices Hugo Komatsu
2026-09-08 14:58 ` John Levon
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