Re: [PATCH 0/2] vfio: Align mmaps

["Cédric Le Goater" <clg@redhat.com>]

On 10/22/24 22:08, Alex Williamson wrote:
> As described in patch /2, newer kernels may support pfnmap with PMD or
> PUD sized mappings.  Mappings must be aligned in order to see the full
> benefit of this support.  We're largely able to get PMD alignment for
> free from mmap, but PUD alignment requires some effort.  Further, we
> don't actually have an easy way to determine PMD or PUD alignment,
> therefore we align all mmaps to the nearest power-of-two relative to the
> region size, up to the maximum PUD size known the be currently available.
> 
> Enabling debug prints in the kernel shows that this exclusively enables
> 1GiB mappings for a GPU with a multi-gigabyte BAR whereas previously the
> BAR is mapped with a combination of 2MiB and 1GiB mappings, only using
> 1GiB when opportunistically crossing an alignment boundary.
> 
> If there are ways to determine discrete alignment intervals or better
> ways to generate a properly aligned address value for mmap, please share.
> Thanks,
> 
> Alex
> 
> Alex Williamson (2):
>    vfio/helpers: Refactor vfio_region_mmap() error handling
>    vfio/helpers: Align mmaps
> 
>   hw/vfio/helpers.c | 66 +++++++++++++++++++++++++++++++++--------------
>   1 file changed, 47 insertions(+), 19 deletions(-)
> 


Applied to vfio-next.

Thanks,

C.