Re: [RFC PATCH 0/7] vfio: Add alias region uapi for device feature

[David Matlack]

On Wed, Sep 24, 2025 at 7:11 AM Mahmoud Adam <mngyadam@xxxxxxxxx> wrote:
>
> This RFC proposes a new uapi VFIO DEVICE_FEATURE to create per-region
> aliases with selectable attributes, initially enabling write-combine
> (WC) where supported by the underlying region. The goal is to expose a
> UAPI for userspace to request an alias of an existing VFIO region with
> extra flags, then interact with it via a stable alias index through
> existing ioctls and mmap where applicable.

Would it make sense to build this on top of Leon's dma-buf series [1]?
My understanding is that dma-buf can support mmap, so WC could just be
a property attached to a dma-buf fd and passed by userspace via
VFIO_DEVICE_FEATURE_DMA_BUF. Then VFIO wouldn't have to create or
manage region aliases.

Apologies if this has already been discussed, I did not go through all
the past discussion.

[1] https://lore.kernel.org/kvm/72ecaa13864ca346797e342d23a7929562788148.1760368250.git.leon@xxxxxxxxxx/