Re: [Qemu-devel] [RFC PATCH 7/8] VFIO: Add new IOCTL for IOMMU TLB invalidate propagation

[Alex Williamson]

On Wed, 26 Apr 2017 18:12:04 +0800
"Liu, Yi L" <address@hidden> wrote:

> From: "Liu, Yi L" <address@hidden>
> 
> This patch adds VFIO_IOMMU_TLB_INVALIDATE to propagate IOMMU TLB
> invalidate request from guest to host.
> 
> In the case of SVM virtualization on VT-d, host IOMMU driver has
> no knowledge of caching structure updates unless the guest
> invalidation activities are passed down to the host. So a new
> IOCTL is needed to propagate the guest cache invalidation through
> VFIO.
> 
> Signed-off-by: Liu, Yi L <address@hidden>
> ---
>  include/uapi/linux/vfio.h | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 6b97987..50c51f8 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -564,6 +564,15 @@ struct vfio_device_svm {
>  
>  #define VFIO_IOMMU_SVM_BIND_TASK     _IO(VFIO_TYPE, VFIO_BASE + 22)
>  
> +/* For IOMMU TLB Invalidation Propagation */
> +struct vfio_iommu_tlb_invalidate {
> +     __u32   argsz;
> +     __u32   length;
> +     __u8    data[];
> +};
> +
> +#define VFIO_IOMMU_TLB_INVALIDATE    _IO(VFIO_TYPE, VFIO_BASE + 23)

I'm kind of wondering why this isn't just a new flag bit on
vfio_device_svm, the data structure is so similar.  Of course data
needs to be fully specified in uapi.

> +
>  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
>  
>  /*