Re: [PATCH v3 2/3] vfio/pci: Support 8-byte PCI loads and stores

[Gerd Bayer <gbayer@linux.ibm.com>]

On Mon, 2024-04-29 at 10:31 -0600, Alex Williamson wrote:
> On Thu, 25 Apr 2024 18:56:03 +0200
> Gerd Bayer <gbayer@linux.ibm.com> wrote:
> 
> > From: Ben Segal <bpsegal@us.ibm.com>
> > 
> > Many PCI adapters can benefit or even require full 64bit read
> > and write access to their registers. In order to enable work on
> > user-space drivers for these devices add two new variations
> > vfio_pci_core_io{read|write}64 of the existing access methods
> > when the architecture supports 64-bit ioreads and iowrites.
> > 
> > Signed-off-by: Ben Segal <bpsegal@us.ibm.com>
> > Co-developed-by: Gerd Bayer <gbayer@linux.ibm.com>
> > Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
> > ---
> >  drivers/vfio/pci/vfio_pci_rdwr.c | 16 ++++++++++++++++
> >  include/linux/vfio_pci_core.h    |  3 +++
> >  2 files changed, 19 insertions(+)
> > 
> > diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c
> > b/drivers/vfio/pci/vfio_pci_rdwr.c
> > index 3335f1b868b1..8ed06edaee23 100644
> > --- a/drivers/vfio/pci/vfio_pci_rdwr.c
> > +++ b/drivers/vfio/pci/vfio_pci_rdwr.c
> > @@ -89,6 +89,9 @@ EXPORT_SYMBOL_GPL(vfio_pci_core_ioread##size);
> >  VFIO_IOREAD(8)
> >  VFIO_IOREAD(16)
> >  VFIO_IOREAD(32)
> > +#ifdef ioread64
> > +VFIO_IOREAD(64)
> > +#endif
> >  
> >  #define
> > VFIO_IORDWR(size)						\
> >  static int vfio_pci_core_iordwr##size(struct vfio_pci_core_device
> > *vdev,\
> > @@ -124,6 +127,10 @@ static int vfio_pci_core_iordwr##size(struct
> > vfio_pci_core_device *vdev,\
> >  VFIO_IORDWR(8)
> >  VFIO_IORDWR(16)
> >  VFIO_IORDWR(32)
> > +#if defined(ioread64) && defined(iowrite64)
> > +VFIO_IORDWR(64)
> > +#endif
> > +
> >  /*
> >   * Read or write from an __iomem region (MMIO or I/O port) with an
> > excluded
> >   * range which is inaccessible.  The excluded range drops writes
> > and fills
> > @@ -148,6 +155,15 @@ ssize_t vfio_pci_core_do_io_rw(struct
> > vfio_pci_core_device *vdev, bool test_mem,
> >  		else
> >  			fillable = 0;
> >  
> > +#if defined(ioread64) && defined(iowrite64)
> 
> Nit, #ifdef vfio_pci_core_iordwr64

I'm sorry, but I'm not sure how I should check for the expanded symbol
here. I think I'll have to stick to checking the same condition as for
whether VFIO_IORDWR(64) should be expanded.

> > +		if (fillable >= 8 && !(off % 8)) {
> > +			ret = vfio_pci_core_iordwr64(vdev,
> > iswrite, test_mem,
> > +						     io, buf, off,
> > &filled);
> > +			if (ret)
> > +				return ret;
> > +
> > +		} else
> > +#endif /* defined(ioread64) && defined(iowrite64) */
> 
> AFAIK, the comment appended to the #endif is really only suggested
> when the code block is too long to reasonable fit in a terminal. 
> That's no longer the case with the new helper.

Yes, I'll change that.

> Thanks,
> 
> Alex
> 
> 

Thanks, Gerd