Re: [PATCH] hw/vfio/common: Trace in which mode a IOMMU is opened

[Auger Eric <eric.auger@redhat.com>]

Hi Philippe,

On 5/26/20 7:35 PM, Philippe Mathieu-Daudé wrote:
> One might want to check which IOMMU version the host kernel
> provide. Add a trace event to see in which mode we opened
> our container.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  hw/vfio/common.c     | 19 ++++++++++++++-----
>  hw/vfio/trace-events |  1 +
>  2 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 0b3593b3c0..6b69a259c1 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -1157,15 +1157,24 @@ static void vfio_put_address_space(VFIOAddressSpace *space)
>  static int vfio_get_iommu_type(VFIOContainer *container,
>                                 Error **errp)
>  {
> -    int iommu_types[] = { VFIO_TYPE1v2_IOMMU, VFIO_TYPE1_IOMMU,
> -                          VFIO_SPAPR_TCE_v2_IOMMU, VFIO_SPAPR_TCE_IOMMU };
> +    static const struct {
> +        int type;
> +        const char *name;
> +    } iommu[] = {
> +        {VFIO_TYPE1v2_IOMMU, "Type1 (v2)"},
> +        {VFIO_TYPE1_IOMMU, "Type1 (v1)"},
> +        {VFIO_SPAPR_TCE_v2_IOMMU, "sPAPR TCE (v2)"},
> +        {VFIO_SPAPR_TCE_IOMMU, "sPAPR TCE (v1)"}
> +    };
>      int i;
>  
> -    for (i = 0; i < ARRAY_SIZE(iommu_types); i++) {
> -        if (ioctl(container->fd, VFIO_CHECK_EXTENSION, iommu_types[i])) {
> -            return iommu_types[i];
> +    for (i = 0; i < ARRAY_SIZE(iommu); i++) {
> +        if (ioctl(container->fd, VFIO_CHECK_EXTENSION, iommu[i].type)) {
> +            trace_vfio_get_iommu_type(iommu[i].type, iommu[i].name);
Just wondering why you want to trace the type as you now have the name
string.
> +            return iommu[i].type;
>          }
>      }
> +    trace_vfio_get_iommu_type(-1, "Not available or not supported");
nit: from a debugging pov, this may be not needed as
vfio_get_group/vfio_connect_container() fails and this leads to an error
output.

Thanks

Eric
>      error_setg(errp, "No available IOMMU models");
>      return -EINVAL;
>  }
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index b1ef55a33f..8166c4c50d 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -115,6 +115,7 @@ vfio_region_sparse_mmap_header(const char *name, int index, int nr_areas) "Devic
>  vfio_region_sparse_mmap_entry(int i, unsigned long start, unsigned long end) "sparse entry %d [0x%lx - 0x%lx]"
>  vfio_get_dev_region(const char *name, int index, uint32_t type, uint32_t subtype) "%s index %d, %08x/%0x8"
>  vfio_dma_unmap_overflow_workaround(void) ""
> +vfio_get_iommu_type(int iommu_type, const char *iommu_name) "IOMMU type %d (%s)"
>  
>  # platform.c
>  vfio_platform_base_device_init(char *name, int groupid) "%s belongs to group #%d"
>