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

[Alex Williamson <alex.williamson@redhat.com>]

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

> +		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.  Thanks,

Alex

>  		if (fillable >= 4 && !(off % 4)) {
>  			ret = vfio_pci_core_iordwr32(vdev, iswrite, test_mem,
>  						     io, buf, off, &filled);
> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
> index a2c8b8bba711..f4cf5fd2350c 100644
> --- a/include/linux/vfio_pci_core.h
> +++ b/include/linux/vfio_pci_core.h
> @@ -157,5 +157,8 @@ int vfio_pci_core_ioread##size(struct vfio_pci_core_device *vdev,	\
>  VFIO_IOREAD_DECLATION(8)
>  VFIO_IOREAD_DECLATION(16)
>  VFIO_IOREAD_DECLATION(32)
> +#ifdef ioread64
> +VFIO_IOREAD_DECLATION(64)
> +#endif
>  
>  #endif /* VFIO_PCI_CORE_H */