[PATCH v1 00/10] DDW indirect mapping

Leonardo Bras
2020-08-17T23:40:58Z

This patchset must be applied on top of:
http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=194179&state=%2A&archive=both

As of today, if the biggest DDW that can be created can't map the whole
partition, it's creation is skipped and the default DMA window
ibm,dma-window" is used instead.

Usually, the available DDW will be 16x bigger than the default DMA window,
as it keep the same page count and raise the page size from 4k to 64k.
Besides the increased window size, it performs better on allocations
bigger than 4k, so it would be nice to use it instead.

Patch #1 replaces hard-coded 4K page size with a variable containing the
correct page size for the window.

Patch #2 makes sure alignment is correct in iommu_*_coherent().

Patch #3 let small allocations use largepool if there is no more space
left in the other pools, thus allowing the whole DMA window to be used by
smaller allocations.

Patch #4 introduces iommu_table_in_use(), and replace manual bit-field
checking where it's used. It will be used for aborting enable_ddw() if
there is any current iommu allocation and we are trying single window
indirect mapping.

Patch #5 introduces iommu_pseries_alloc_table() that will be helpful
when indirect mapping needs to replace the iommu_table.

Patch #6 adds helpers for adding and removing DDWs in the list.

Patch #7 refactors enable_ddw() so it returns if direct mapping is
possible, instead of DMA offset. It helps for next patches on
indirect DMA mapping and also allows DMA windows starting at 0x00.

Patch #8 bring new helper to simplify enable_ddw(), allowing
some reorganization for introducing indirect mapping DDW.

Patch #9:
Instead of destroying the created DDW if it doesn't map the whole
partition, make use of it instead of the default DMA window as it improves
performance. Also, update the iommu_table and re-generate the pools.

Patch #10:
Does some renaming of 'direct window' to 'dma window', given the DDW
created can now be also used in indirect mapping if direct mapping is not
available.

All patches were tested into an LPAR with an Ethernet VF:
4005:01:00.0 Ethernet controller: Mellanox Technologies MT27700 Family
[ConnectX-4 Virtual Function]

Patchset was tested with a 64GB DDW which did not map the whole
partition (128G).

Leonardo Bras (10):
powerpc/pseries/iommu: Replace hard-coded page shift
powerpc/kernel/iommu: Align size for IOMMU_PAGE_SIZE on
iommu_*_coherent()
powerpc/kernel/iommu: Use largepool as a last resort when !largealloc
powerpc/kernel/iommu: Add new iommu_table_in_use() helper
powerpc/pseries/iommu: Add iommu_pseries_alloc_table() helper
powerpc/pseries/iommu: Add ddw_list_add() helper
powerpc/pseries/iommu: Allow DDW windows starting at 0x00
powerpc/pseries/iommu: Add ddw_property_create() and refactor
enable_ddw()
powerpc/pseries/iommu: Make use of DDW even if it does not map the
partition
powerpc/pseries/iommu: Rename "direct window" to "dma window"

arch/powerpc/include/asm/iommu.h | 1 +
arch/powerpc/include/asm/tce.h | 10 +-
arch/powerpc/kernel/iommu.c | 88 +++---
arch/powerpc/platforms/pseries/iommu.c | 394 ++++++++++++++++---------
4 files changed, 305 insertions(+), 188 deletions(-)

--
2.25.4