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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 5/27/20 9:08 AM, Auger Eric wrote:
> 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.

You are right :)

>> +            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.

Indeed.

Thanks for the review!

> 
> 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"
>>
>