[RFC PATCH v2 0/6] powerpc: pSeries: vfio: iommu: Re-enable support for SPAPR TCE VFIO

Shivaprasad G Bhat
2024-04-30T20:06:15Z

RFC v1 was posted here [1]. As I was testing more and fixing the
issues, I realized its clean to have the table_group_ops implemented
the way it is done on PowerNV and stop 'borrowing' the DMA windows
for pSeries.

This patch-set implements the iommu table_group_ops for pSeries for
VFIO SPAPR TCE sub-driver thereby enabling the VFIO support on POWER
pSeries machines.

So, this patchset is a re-write and not close to the V1 except
for few changes.

Structure of the patchset:
-------------------------
The first and fifth patches just code movements.

Second patch takes care of collecting the TCE and DDW information
for the vfio_iommu_spapr_tce_ddw_info during probe.

Third patch fixes the convention of using table[1] for VFs on
pSeries when used by the host driver.

Fourth patch fixes the VFIO to call TCE clear before unset window.

The last patch has the API implementations, please find the
details on its commit description.

Testing:
-------
Tested with nested guest for NVME card, Mellanox multi-function
card by attaching them to nested kvm guest running on a pSeries
lpar.
Also vfio-test [2] by Alex Willamson, was forked and updated to
add support for pSeries guest and used to test these patches[3].

Limitations/Known Issues:
------------------------
* The DMA window restrictions with SRIOV VF scenarios of having
maximum 1 dma window is taken care in the current patches itself.
However, the necessary changes required in
vfio_iommu_spapr_tce_ddw_info to expose the default window being
a 64-bit one and the qemu changes handle the same will be taken
care in next versions.
* KVM guest boot throws warning at remap_pfn_range_notrack(), on
the host, I will post the fix along in the next versions.
* The DLPAR hotplugged device has no FDT entry until next reboot,
default dma window property has to be preserved differently for
this case.

References:
----------
[1] https://lore.kernel.org/linuxppc-dev/171026724548.8367.8321359354119254395.stgit@linux.ibm.com/
[2] https://github.com/awilliam/tests
[3] https://github.com/nnmwebmin/vfio-ppc-tests/tree/vfio-ppc-ex

---
Changelog:
v1: https://lore.kernel.org/linuxppc-dev/171026724548.8367.8321359354119254395.stgit@linux.ibm.com/
- Rewrite as to stop borrowing the DMA windows and implemented
the table_group_ops for pSeries.
- Cover letter and Patch 6 has more details as this was a rewrite.

Shivaprasad G Bhat (6):
powerpc/iommu: Move pSeries specific functions to pseries/iommu.c
powerpc/pseries/iommu: Fix the VFIO_IOMMU_SPAPR_TCE_GET_INFO ioctl output
powerpc/pseries/iommu: Use the iommu table[0] for IOV VF's DDW
vfio/spapr: Always clear TCEs before unsetting the window
powerpc/iommu: Move dev_has_iommu_table() to iommu.c
powerpc/iommu: Implement the iommu_table_group_ops for pSeries

arch/powerpc/include/asm/iommu.h | 9 +-
arch/powerpc/kernel/eeh.c | 16 -
arch/powerpc/kernel/iommu.c | 170 +----
arch/powerpc/platforms/powernv/pci-ioda.c | 6 +-
arch/powerpc/platforms/pseries/iommu.c | 720 +++++++++++++++++++++-
drivers/vfio/vfio_iommu_spapr_tce.c | 13 +-
6 files changed, 729 insertions(+), 205 deletions(-)

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