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

[Alex Williamson <alex.williamson@redhat.com>]

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,

Alex