Re: [PATCH v2] hw/vfio/common: Trace in which mode an IOMMU is opened

[Philippe Mathieu-Daudé]

On 6/9/20 7:33 PM, Alex Williamson wrote:
> On Tue, 9 Jun 2020 19:23:32 +0200
> Laurent Vivier <laurent@vivier.eu> wrote:
> 
>> Le 27/05/2020 à 17:55, Philippe Mathieu-Daudé a écrit :
>>> 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.
>>>
>>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>> ---
>>> v2: Only display string description (Eric)
>>>
>>> Supersedes: <20200526173542.28710-1-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..f24450472e 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].name);
>>> +            return iommu[i].type;
>>>          }
>>>      }
>>> +    trace_vfio_get_iommu_type("Not available or not supported");
>>>      error_setg(errp, "No available IOMMU models");
>>>      return -EINVAL;
>>>  }
>>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
>>> index b1ef55a33f..d3f1e48618 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(const char *type) "IOMMU type: %s"
>>>  
>>>  # platform.c
>>>  vfio_platform_base_device_init(char *name, int groupid) "%s belongs to 
>>> group #%d"
>>>   
>>
>> Applied to my trivial-patches branch.
> 
> I was not actually a fan of this patch:
> 
> https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg08144.html
> 
> I don't think the convenience to the trace user to avoid looking up the
> type string in the header is worth the bloat to the non-trace user to
> declare these strings in the code.  Thanks,

Yep, planned to send simpler v3 but re-prioritize stuffs...