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

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

On 5/27/20 9:43 AM, Philippe Mathieu-Daudé wrote:
> 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.

But you can reach this for example using No-IOMMU. If you don't mind, I
find having this information in the trace log clearer.

> 
> 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"
>>>
>>
>