Re: [RFC PATCH 8/8] vfio/pci: Clear VFIO_IRQ_INFO_NORESIZE for MSI-X

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

On Wed, 15 Mar 2023 13:59:28 -0700
Reinette Chatre <reinette.chatre@intel.com> wrote:

> Dynamic MSI-X is supported. Clear VFIO_IRQ_INFO_NORESIZE
> to provide guidance to user space.
> 
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> ---
>  drivers/vfio/pci/vfio_pci_core.c | 2 +-
>  include/uapi/linux/vfio.h        | 3 +++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index ae0e161c7fc9..1d071ee212a7 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1111,7 +1111,7 @@ static int vfio_pci_ioctl_get_irq_info(struct vfio_pci_core_device *vdev,
>  	if (info.index == VFIO_PCI_INTX_IRQ_INDEX)
>  		info.flags |=
>  			(VFIO_IRQ_INFO_MASKABLE | VFIO_IRQ_INFO_AUTOMASKED);
> -	else
> +	else if (info.index != VFIO_PCI_MSIX_IRQ_INDEX)
>  		info.flags |= VFIO_IRQ_INFO_NORESIZE;
>  

I think we need to check pci_msix_can_alloc_dyn(), right?  Thanks,

Alex

>  	return copy_to_user(arg, &info, minsz) ? -EFAULT : 0;
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 0552e8dcf0cb..1a36134cae5c 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -511,6 +511,9 @@ struct vfio_region_info_cap_nvlink2_lnkspd {
>   * then add and unmask vectors, it's up to userspace to make the decision
>   * whether to allocate the maximum supported number of vectors or tear
>   * down setup and incrementally increase the vectors as each is enabled.
> + * Absence of the NORESIZE flag indicates that vectors can be enabled
> + * and disabled dynamically without impacting other vectors within the
> + * index.
>   */
>  struct vfio_irq_info {
>  	__u32	argsz;