Re: [PATCH v2 05/10] iommupt: Add the Intel VT-D second stage page table format

[Baolu Lu <baolu.lu@linux.intel.com>]

On 8/27/25 01:26, Jason Gunthorpe wrote:
> The VT-D second stage format is almost the same as the x86 PAE format,
> except the bit encodings in the PTE are different and a few new PTE
> features, like force coherency are present.
> 
> Among all the formats it is unique in not having a designated present bit.
> 
> Comparing the performance of several operations to the existing version:
> 
> iommu_map()
>     pgsz  ,avg new,old ns, min new,old ns  , min % (+ve is better)
>       2^12,     53,66    ,      50,64      ,  21.21
>       2^21,     59,70    ,      56,67      ,  16.16
>       2^30,     54,66    ,      52,63      ,  17.17
>   256*2^12,    384,524   ,     337,516     ,  34.34
>   256*2^21,    387,632   ,     336,626     ,  46.46
>   256*2^30,    376,629   ,     323,623     ,  48.48
> 
> iommu_unmap()
>     pgsz  ,avg new,old ns, min new,old ns  , min % (+ve is better)
>       2^12,     67,86    ,      63,84      ,  25.25
>       2^21,     64,84    ,      59,80      ,  26.26
>       2^30,     59,78    ,      56,74      ,  24.24
>   256*2^12,    216,335   ,     198,317     ,  37.37
>   256*2^21,    245,350   ,     232,344     ,  32.32
>   256*2^30,    248,345   ,     226,339     ,  33.33
> 
> Cc: Tina Zhang<tina.zhang@intel.com>
> Cc: Kevin Tian<kevin.tian@intel.com>
> Cc: Lu Baolu<baolu.lu@linux.intel.com>
> Signed-off-by: Jason Gunthorpe<jgg@nvidia.com>
> ---
>   drivers/iommu/generic_pt/.kunitconfig      |   1 +
>   drivers/iommu/generic_pt/Kconfig           |  11 +
>   drivers/iommu/generic_pt/fmt/Makefile      |   2 +
>   drivers/iommu/generic_pt/fmt/defs_vtdss.h  |  21 ++
>   drivers/iommu/generic_pt/fmt/iommu_vtdss.c |  10 +
>   drivers/iommu/generic_pt/fmt/vtdss.h       | 289 +++++++++++++++++++++
>   include/linux/generic_pt/common.h          |  18 ++
>   include/linux/generic_pt/iommu.h           |  11 +
>   8 files changed, 363 insertions(+)
>   create mode 100644 drivers/iommu/generic_pt/fmt/defs_vtdss.h
>   create mode 100644 drivers/iommu/generic_pt/fmt/iommu_vtdss.c
>   create mode 100644 drivers/iommu/generic_pt/fmt/vtdss.h

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>