Re: [PATCH v2 1/3] vfio: Find DMA available capability

[Cornelia Huck <cohuck@redhat.com>]

On Tue, 15 Sep 2020 09:57:03 -0400
Matthew Rosato <mjrosato@linux.ibm.com> wrote:

> On 9/15/20 6:33 AM, Cornelia Huck wrote:
> > On Mon, 14 Sep 2020 18:29:28 -0400
> > Matthew Rosato <mjrosato@linux.ibm.com> wrote:
> >   
> >> The underlying host may be limiting the number of outstanding DMA
> >> requests for type 1 IOMMU.  Add helper functions to check for the
> >> DMA available capability and retrieve the current number of DMA
> >> mappings allowed.
> >>
> >> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> >> ---
> >>   hw/vfio/common.c              | 37 +++++++++++++++++++++++++++++++++++++
> >>   include/hw/vfio/vfio-common.h |  2 ++
> >>   2 files changed, 39 insertions(+)
> >>  
> > 
> > (...)
> >   
> >> +bool vfio_get_info_dma_avail(struct vfio_iommu_type1_info *info,
> >> +                             unsigned int *avail)
> >> +{
> >> +    struct vfio_info_cap_header *hdr;
> >> +    struct vfio_iommu_type1_info_dma_avail *cap;
> >> +
> >> +    /* If the capability cannot be found, assume no DMA limiting */
> >> +    hdr = vfio_get_iommu_type1_info_cap(info,
> >> +                                        VFIO_IOMMU_TYPE1_INFO_DMA_AVAIL);  
> > 
> > ...don't you need a headers sync first to get the new definitions?
> >   
> 
> You are right of course, though the associated header change is not yet 
> merged in the kernel so it's a bit flaky.  But bottom line:  yes, we 
> need a header sync first, I'll include one in v3.

Just include a placeholder patch :) It's easy to replace them with a
real update prior to merging.