Re: [PATCH v3 4/5] s390x/pci: Add routine to get the vfio dma available count

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 16 Sep 2020 09:21:39 +0200
Philippe Mathieu-Daudé <philmd@redhat.com> wrote:

> On 9/15/20 9:14 PM, Matthew Rosato wrote:
> > Create new files for separating out vfio-specific work for s390
> > pci. Add the first such routine, which issues VFIO_IOMMU_GET_INFO
> > ioctl to collect the current dma available count.
> > 
> > Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> > ---
> >  hw/s390x/meson.build     |  1 +
> >  hw/s390x/s390-pci-vfio.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  hw/s390x/s390-pci-vfio.h | 17 +++++++++++++++
> >  3 files changed, 72 insertions(+)
> >  create mode 100644 hw/s390x/s390-pci-vfio.c
> >  create mode 100644 hw/s390x/s390-pci-vfio.h
> > 

(...)

> > diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
> > new file mode 100644
> > index 0000000..75e3ac1
> > --- /dev/null
> > +++ b/hw/s390x/s390-pci-vfio.c
> > @@ -0,0 +1,54 @@
> > +/*
> > + * s390 vfio-pci interfaces
> > + *
> > + * Copyright 2020 IBM Corp.
> > + * Author(s): Matthew Rosato <mjrosato@linux.ibm.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or (at
> > + * your option) any later version. See the COPYING file in the top-level
> > + * directory.
> > + */
> > +
> > +#include <sys/ioctl.h>
> > +
> > +#include "qemu/osdep.h"
> > +#include "s390-pci-vfio.h"
> > +#include "hw/vfio/vfio-common.h"
> > +
> > +/*
> > + * Get the current DMA available count from vfio.  Returns true if vfio is
> > + * limiting DMA requests, false otherwise.  The current available count read
> > + * from vfio is returned in avail.
> > + */
> > +bool s390_pci_update_dma_avail(int fd, unsigned int *avail)
> > +{
> > +    g_autofree struct vfio_iommu_type1_info *info;
> > +    uint32_t argsz;
> > +    int ret;
> > +
> > +    assert(avail);
> > +
> > +    argsz = sizeof(struct vfio_iommu_type1_info);
> > +    info = g_malloc0(argsz);
> > +    info->argsz = argsz;
> > +    /*
> > +     * If the specified argsz is not large enough to contain all
> > +     * capabilities it will be updated upon return.  In this case
> > +     * use the updated value to get the entire capability chain.
> > +     */
> > +    ret = ioctl(fd, VFIO_IOMMU_GET_INFO, info);
> > +    if (argsz != info->argsz) {
> > +        argsz = info->argsz;
> > +        info = g_realloc(info, argsz);  
> 
> Do we need to bzero [sizeof(struct vfio_iommu_type1_info)..argsz[?

If we do, I think we need to do the equivalent in
vfio_get_region_info() as well?

(Also, shouldn't we check ret before looking at info->argsz?)

> 
> > +        info->argsz = argsz;
> > +        ret = ioctl(fd, VFIO_IOMMU_GET_INFO, info);
> > +    }
> > +
> > +    if (ret) {
> > +        return false;
> > +    }
> > +
> > +    /* If the capability exists, update with the current value */
> > +    return vfio_get_info_dma_avail(info, avail);
> > +}
> > +

(...)