Re: [Qemu-devel] [RFC PATCH qemu 1/3] memory: Add get_fd() hook for IOMMU MR

[Alex Williamson]

On Tue, 28 Mar 2017 20:05:28 +1100
Alexey Kardashevskiy <address@hidden> wrote:

> Signed-off-by: Alexey Kardashevskiy <address@hidden>
> ---
>  include/exec/memory.h | 2 ++
>  hw/ppc/spapr_iommu.c  | 8 ++++++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index e39256ad03..925c10b35b 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -174,6 +174,8 @@ struct MemoryRegionIOMMUOps {
>      void (*notify_flag_changed)(MemoryRegion *iommu,
>                                  IOMMUNotifierFlag old_flags,
>                                  IOMMUNotifierFlag new_flags);
> +    /* Returns a kernel fd for IOMMU */
> +    int (*get_fd)(MemoryRegion *iommu);

What if we used this as a prototype:

int (*get_fd)(IOMMUFdType type, MemoryRegion *iommu);

And then we defined:

typedef enum {
    SPAPR_IOMMU_TABLE_FD = 0,
} IOMMUFdType;

Such that you're actually asking the IOMMUOps for a specific type of FD
and it either has it or not, so the caller doesn't need to assume what
it is they get back.

Furthermore, add:

int memory_region_iommu_get_fd(IOMMUFdType type, MemoryRegion *mr)
{
    assert(memory_region_is_iommu(mr));

    if (mr->iommu_ops && mr->iommu_ops->get_fd) {
        return mr->iommu_ops->get_fd(type, mr);
    }

    return -1;
}

>  };
>

This should be two patches, patch 1 above, patch 2 below
  
>  typedef struct CoalescedMemoryRange CoalescedMemoryRange;
> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> index 9e30e148d6..b61c8f053e 100644
> --- a/hw/ppc/spapr_iommu.c
> +++ b/hw/ppc/spapr_iommu.c
> @@ -170,6 +170,13 @@ static void spapr_tce_notify_flag_changed(MemoryRegion 
> *iommu,
>      }
>  }
>  
> +static int spapr_tce_get_fd(MemoryRegion *iommu)
> +{
> +    sPAPRTCETable *tcet = container_of(iommu, sPAPRTCETable, iommu);
> +
> +    return tcet->fd;


This would then be:

    return type == SPAPR_IOMMU_TABLE_FD ? tcet->fd : -1;

> +}
> +
>  static int spapr_tce_table_post_load(void *opaque, int version_id)
>  {
>      sPAPRTCETable *tcet = SPAPR_TCE_TABLE(opaque);
> @@ -251,6 +258,7 @@ static MemoryRegionIOMMUOps spapr_iommu_ops = {
>      .translate = spapr_tce_translate_iommu,
>      .get_min_page_size = spapr_tce_get_min_page_size,
>      .notify_flag_changed = spapr_tce_notify_flag_changed,
> +    .get_fd = spapr_tce_get_fd,
>  };
>  
>  static int spapr_tce_table_realize(DeviceState *dev)