Re: [PATCH 11/14] vfio: add vfio_pci_config_space_read/write()

[John Levon <john.levon@nutanix.com>]

On Wed, Apr 09, 2025 at 11:51:09PM +0800, Tomita Moeko wrote:

> On 4/9/25 21:48, John Levon wrote:
> > Add these helpers that access config space and return an -errno style
> > return.
> > 
> > Signed-off-by: John Levon <john.levon@nutanix.com>
> > ---
> >  hw/vfio/pci.c | 134 ++++++++++++++++++++++++++++++++++----------------
> >  1 file changed, 91 insertions(+), 43 deletions(-)
> > 
> > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> > index ddeee33aa9..c3842d2f8d 100644
> > --- a/hw/vfio/pci.c
> > +++ b/hw/vfio/pci.c
> > @@ -964,6 +964,28 @@ static void vfio_pci_load_rom(VFIOPCIDevice *vdev)
> >      }
> >  }
> >  
> > +/* "Raw" read of underlying config space. */
> > +static int vfio_pci_config_space_read(VFIOPCIDevice *vdev, off_t offset,
> > +                                      uint32_t size, void *data)
> 
> Returning ssize_t here might be better here to avoid casting issues,
> though we would never read/write something exceeds INT32_MAX.

I considered this (and the later helpers in the patch), but most of the existing
code already uses int. Happy to look at fixing the callers too (e.g.
vfio_msi_setup()) if that's everyone's preference.

regards
john