Re: [RFC, v0 1/3] vfio/platform: add support for msi

Alex Williamson
2020-11-05T07:08:22Z

On Thu, 5 Nov 2020 11:32:55 +0530
Vikas Gupta <vikas.gupta@broadcom.com> wrote:

> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 2f313a238a8f..aab051e8338d 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -203,6 +203,7 @@ struct vfio_device_info {
> #define VFIO_DEVICE_FLAGS_AP (1 << 5) /* vfio-ap device */
> #define VFIO_DEVICE_FLAGS_FSL_MC (1 << 6) /* vfio-fsl-mc device */
> #define VFIO_DEVICE_FLAGS_CAPS (1 << 7) /* Info supports caps */
> +#define VFIO_DEVICE_FLAGS_MSI (1 << 8) /* Device supports msi */
> __u32 num_regions; /* Max region index + 1 */
> __u32 num_irqs; /* Max IRQ index + 1 */
> __u32 cap_offset; /* Offset within info struct of first cap */

This doesn't make any sense to me, MSIs are just edge triggered
interrupts to userspace, so why isn't this fully described via
VFIO_DEVICE_GET_IRQ_INFO? If we do need something new to describe it,
this seems incomplete, which indexes are MSI (IRQ_INFO can describe
that)? We also already support MSI with vfio-pci, so a global flag for
the device advertising this still seems wrong. Thanks,

Alex