Re: [PATCH] vfio/pci: Add iowrite64 and ioread64 support for vfio pci

Jason Gunthorpe
2024-05-24T14:00:16Z

On Wed, May 22, 2024 at 04:21:25PM -0700, Ramesh Thomas wrote:
> ioread64 and iowrite64 macros called by vfio pci implementations are
> defined in asm/io.h if CONFIG_GENERIC_IOMAP is not defined. Include
> linux/io-64-nonatomic-lo-hi.h to define iowrite64 and ioread64 macros
> when they are not defined. io-64-nonatomic-lo-hi.h maps the macros to
> generic implementation in lib/iomap.c. The generic implementation
> does 64 bit rw if readq/writeq is defined for the architecture,
> otherwise it would do 32 bit back to back rw.
>
> Note that there are two versions of the generic implementation that
> differs in the order the 32 bit words are written if 64 bit support is
> not present. This is not the little/big endian ordering, which is
> handled separately. This patch uses the lo followed by hi word ordering
> which is consistent with current back to back implementation in the
> vfio/pci code.
>
> Refer patch series the requirement originated from:
> https://lore.kernel.org/all/20240522150651.1999584-1-gbayer@linux.ibm.com/
>
> Signed-off-by: Ramesh Thomas <ramesh.thomas@intel.com>
> ---
> drivers/vfio/pci/vfio_pci_priv.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h
> index 5e4fa69aee16..5eab5abf2ff2 100644
> --- a/drivers/vfio/pci/vfio_pci_priv.h
> +++ b/drivers/vfio/pci/vfio_pci_priv.h
> @@ -3,6 +3,7 @@
> #define VFIO_PCI_PRIV_H
>
> #include <linux/vfio_pci_core.h>
> +#include <linux/io-64-nonatomic-lo-hi.h>

Why include it here though?

It should go in vfio_pci_rdwr.c and this patch should remove all the
"#ifdef iowrite64"'s from that file too.

But the idea looks right to me

Thanks,
Jason