Hi,
This patch set adds:
* New IOCTL VFIO_IOMMU_DIRTY_PAGES to get dirty pages bitmap with
respect to IOMMU container rather than per device. All pages pinned by
vendor driver through vfio_pin_pages external API has to be marked as
dirty during migration. When IOMMU capable device is present in the
container and all pages are pinned and mapped, then all pages are marked
dirty.
When there are CPU writes, CPU dirty page tracking can identify dirtied
pages, but any page pinned by vendor driver can also be written by
device. As of now there is no device which has hardware support for
dirty page tracking. So all pages which are pinned should be considered
as dirty.
This ioctl is also used to start dirty pages tracking for unpinned pages
while migration is active and device is running. These tracked unpinned
pages information is cleaned on dirty bitmap read from VFIO application
or if migration is failed or cancelled and unpinned pages tracking is
stopped.
* Updated IOCTL VFIO_IOMMU_UNMAP_DMA to get dirty pages bitmap before
unmapping IO virtual address range.
With vIOMMU, during pre-copy phase of migration, while CPUs are still
running, IO virtual address unmap can happen while device still keeping
reference of guest pfns. Those pages should be reported as dirty before
unmap, so that VFIO user space application can copy content of those
pages from source to destination.
Yet TODO:
Since there is no device which has hardware support for system memmory
dirty bitmap tracking, right now there is no other API from vendor driver
to VFIO IOMMU module to report dirty pages. In future, when such hardware
support will be implemented, an API will be required such that vendor
driver could report dirty pages to VFIO module during migration phases.
If IOMMU capable device is present in the container, then all pages are
marked dirty. Need to think smart way to know if IOMMU capable device's
driver is smart to report pages to be marked dirty by pinning those pages
externally.
Adding revision history from previous QEMU patch set to understand KABI
changes done till now
v9 -> v10:
- Updated existing VFIO_IOMMU_UNMAP_DMA ioctl to get dirty pages bitmap
during unmap while migration is active
- Added flag in VFIO_IOMMU_GET_INFO to indicate driver support dirty page
tracking.
- If iommu_mapped, mark all pages dirty.
- Added unpinned pages tracking while migration is active.
- Updated comments for migration device state structure with bit
combination table and state transition details.
v8 -> v9:
- Split patch set in 2 sets, Kernel and QEMU.
- Dirty pages bitmap is queried from IOMMU container rather than from
vendor driver for per device. Added 2 ioctls to achieve this.
v7 -> v8:
- Updated comments for KABI
- Added BAR address validation check during PCI device's config space load
as suggested by Dr. David Alan Gilbert.
- Changed vfio_migration_set_state() to set or clear device state flags.
- Some nit fixes.
v6 -> v7:
- Fix build failures.
v5 -> v6:
- Fix build failure.
v4 -> v5:
- Added decriptive comment about the sequence of access of members of
structure vfio_device_migration_info to be followed based on Alex's
suggestion
- Updated get dirty pages sequence.
- As per Cornelia Huck's suggestion, added callbacks to VFIODeviceOps to
get_object, save_config and load_config.
- Fixed multiple nit picks.
- Tested live migration with multiple vfio device assigned to a VM.
v3 -> v4:
- Added one more bit for _RESUMING flag to be set explicitly.
- data_offset field is read-only for user space application.
- data_size is read for every iteration before reading data from migration,
that is removed assumption that data will be till end of migration
region.
- If vendor driver supports mappable sparsed region, map those region
during setup state of save/load, similarly unmap those from cleanup
routines.
- Handles race condition that causes data corruption in migration region
during save device state by adding mutex and serialiaing save_buffer and
get_dirty_pages routines.
- Skip called get_dirty_pages routine for mapped MMIO region of device.
- Added trace events.
- Split into multiple functional patches.
v2 -> v3:
- Removed enum of VFIO device states. Defined VFIO device state with 2
bits.
- Re-structured vfio_device_migration_info to keep it minimal and defined
action on read and write access on its members.
v1 -> v2:
- Defined MIGRATION region type and sub-type which should be used with
region type capability.
- Re-structured vfio_device_migration_info. This structure will be placed
at 0th offset of migration region.
- Replaced ioctl with read/write for trapped part of migration region.
- Added both type of access support, trapped or mmapped, for data section
of the region.
- Moved PCI device functions to pci file.
- Added iteration to get dirty page bitmap until bitmap for all requested
pages are copied.
Thanks,
Kirti
Kirti Wankhede (5):
vfio: KABI for migration interface for device state
vfio iommu: Adds flag to indicate dirty pages tracking capability
support
vfio iommu: Add ioctl defination for dirty pages tracking.
vfio iommu: Implementation of ioctl to for dirty pages tracking.
vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap
drivers/vfio/vfio_iommu_type1.c | 276 +++++++++++++++++++++++++++++++++++++---
include/uapi/linux/vfio.h | 240 +++++++++++++++++++++++++++++++++-
2 files changed, 499 insertions(+), 17 deletions(-)
--
2.7.0
