Re: [PATCH v2] VT-d: Don't assume register-based invalidation is always supported

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Apr 02, 2020 at 04:06:06AM +0800, Chao Gao wrote:
> --- a/xen/drivers/passthrough/vtd/qinval.c
> +++ b/xen/drivers/passthrough/vtd/qinval.c
> @@ -442,6 +442,23 @@ int enable_qinval(struct vtd_iommu *iommu)
>      return 0;
>  }
>  
> +static int vtd_flush_context_noop(struct vtd_iommu *iommu, uint16_t did,
> +                                  uint16_t source_id, uint8_t function_mask,
> +                                  uint64_t type, bool 
> flush_non_present_entry)
> +{
> +    dprintk(XENLOG_ERR VTDPREFIX, "IOMMU: Cannot flush CONTEXT.\n");
> +    return -EIO;
> +}
> +
> +static int vtd_flush_iotlb_noop(struct vtd_iommu *iommu, uint16_t did,
> +                                uint64_t addr, unsigned int size_order,
> +                                uint64_t type, bool flush_non_present_entry,
> +                                bool flush_dev_iotlb)
> +{
> +    dprintk(XENLOG_ERR VTDPREFIX, "IOMMU: Cannot flush IOTLB.\n");
> +    return -EIO;
> +}

I think I would add an ASSERT_UNREACHABLE() to both noop handlers
above, as I would expect trying to use them without the proper mode
being configured would point to an error elsewhere?

Thanks, Roger.