Re: [PATCH v5 7/9] vfio/pci: Clean up BAR zap and revocation

[Pranjal Shrivastava <praan@google.com>]

On Wed, Jul 15, 2026 at 06:47:30PM +0100, Matt Evans wrote:
> Previously, vfio_pci_zap_bars() (and the wrapper
> vfio_pci_zap_and_down_write_memory_lock()) calls were paired with
> calls to vfio_pci_dma_buf_move().
> 
> This commit replaces them with a unified new function,
> vfio_pci_revoke_bars() containing both the vfio_pci_dma_buf_move() and
> the unmap_mapping_range(), making it harder for callers to omit one.
> It adds a wrapper, vfio_pci_lock_revoke_bars(), which takes the write
> memory_lock before zapping, and adds a new vfio_pci_unrevoke_bars()
> for the re-enable path.
> 
> As of "vfio/pci: Convert BAR mmap() to use a DMABUF", the zap via
> unmap_mapping_range() is no longer performed for vfio-pci since the
> DMABUFs used for BAR mappings already zap PTEs when the
> vfio_pci_dma_buf_move() occurs.
> 
> However, it must be assumed that VFIO drivers which override the .mmap
> op could create mappings _not_ backed by DMABUFs.  So, the zap is
> still performed on revoke if .mmap is overridden, using a new
> zap_bars_on_revoke flag.  A driver can explicitly opt out; the flag is
> cleared by the hisi_acc_vfio_pci driver, since its .mmap just wraps
> vfio_pci_core_mmap() and so still uses DMABUFs.
> 
> Signed-off-by: Matt Evans <matt@ozlabs.org>

Reviewed-by: Pranjal Shrivastava <praan@google.com>

Thanks
Praan