diff mbox series

[PULL,v3,23/32] s390x/pci: Add routine to get the vfio dma available count

Message ID 160426454077.24886.1574050205264167707.stgit@gimli.home
State New
Headers show
Series [PULL,v3,01/32] vfio: Add function to unmap VFIO region | expand

Commit Message

Alex Williamson Nov. 1, 2020, 9:02 p.m. UTC
From: Matthew Rosato <mjrosato@linux.ibm.com>

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>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
[aw: Fix non-Linux build with CONFIG_LINUX]
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 hw/s390x/meson.build             |    1 +
 hw/s390x/s390-pci-vfio.c         |   54 ++++++++++++++++++++++++++++++++++++++
 include/hw/s390x/s390-pci-vfio.h |   24 +++++++++++++++++
 3 files changed, 79 insertions(+)
 create mode 100644 hw/s390x/s390-pci-vfio.c
 create mode 100644 include/hw/s390x/s390-pci-vfio.h

Comments

Philippe Mathieu-Daudé Nov. 3, 2020, 5:49 a.m. UTC | #1
Hi Matthew,

On 11/1/20 10:02 PM, Alex Williamson wrote:
> From: Matthew Rosato <mjrosato@linux.ibm.com>
> 
> 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>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> [aw: Fix non-Linux build with CONFIG_LINUX]
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  hw/s390x/meson.build             |    1 +
>  hw/s390x/s390-pci-vfio.c         |   54 ++++++++++++++++++++++++++++++++++++++
>  include/hw/s390x/s390-pci-vfio.h |   24 +++++++++++++++++
>  3 files changed, 79 insertions(+)
>  create mode 100644 hw/s390x/s390-pci-vfio.c
>  create mode 100644 include/hw/s390x/s390-pci-vfio.h
> 
> diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
> index 948ceae7a7b3..f4663a835514 100644
> --- a/hw/s390x/meson.build
> +++ b/hw/s390x/meson.build
> @@ -27,6 +27,7 @@ s390x_ss.add(when: 'CONFIG_KVM', if_true: files(
>  ))
>  s390x_ss.add(when: 'CONFIG_S390_CCW_VIRTIO', if_true: files('s390-virtio-ccw.c'))
>  s390x_ss.add(when: 'CONFIG_TERMINAL3270', if_true: files('3270-ccw.c'))
> +s390x_ss.add(when: 'CONFIG_LINUX', if_true: files('s390-pci-vfio.c'))
>  
>  virtio_ss = ss.source_set()
>  virtio_ss.add(files('virtio-ccw.c'))
> diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
> new file mode 100644
> index 000000000000..cb3f4d98adf8
> --- /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 "hw/s390x/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;
> +
> +    assert(avail);
> +
> +    argsz = sizeof(struct vfio_iommu_type1_info);
> +    info = g_malloc0(argsz);
> +
> +    /*
> +     * If the specified argsz is not large enough to contain all capabilities
> +     * it will be updated upon return from the ioctl.  Retry until we have
> +     * a big enough buffer to hold the entire capability chain.
> +     */
> +retry:
> +    info->argsz = argsz;
> +
> +    if (ioctl(fd, VFIO_IOMMU_GET_INFO, info)) {
> +        return false;
> +    }
> +
> +    if (info->argsz > argsz) {
> +        argsz = info->argsz;
> +        info = g_realloc(info, argsz);
> +        goto retry;
> +    }
> +
> +    /* If the capability exists, update with the current value */
> +    return vfio_get_info_dma_avail(info, avail);
> +}

--without-default-devices configuration is broken, bisected
to this commit:

hw/s390x/s390-pci-vfio.c:52: undefined reference to
`vfio_get_info_dma_avail'

Can you have a look please?

Thanks.
Cornelia Huck Nov. 3, 2020, 10:45 a.m. UTC | #2
On Tue, 3 Nov 2020 06:49:13 +0100
Philippe Mathieu-Daudé <philmd@redhat.com> wrote:

> Hi Matthew,
> 
> On 11/1/20 10:02 PM, Alex Williamson wrote:
> > From: Matthew Rosato <mjrosato@linux.ibm.com>
> > 
> > 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>
> > Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> > [aw: Fix non-Linux build with CONFIG_LINUX]
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > ---
> >  hw/s390x/meson.build             |    1 +
> >  hw/s390x/s390-pci-vfio.c         |   54 ++++++++++++++++++++++++++++++++++++++
> >  include/hw/s390x/s390-pci-vfio.h |   24 +++++++++++++++++
> >  3 files changed, 79 insertions(+)
> >  create mode 100644 hw/s390x/s390-pci-vfio.c
> >  create mode 100644 include/hw/s390x/s390-pci-vfio.h
> > 
> > diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
> > index 948ceae7a7b3..f4663a835514 100644
> > --- a/hw/s390x/meson.build
> > +++ b/hw/s390x/meson.build
> > @@ -27,6 +27,7 @@ s390x_ss.add(when: 'CONFIG_KVM', if_true: files(
> >  ))
> >  s390x_ss.add(when: 'CONFIG_S390_CCW_VIRTIO', if_true: files('s390-virtio-ccw.c'))
> >  s390x_ss.add(when: 'CONFIG_TERMINAL3270', if_true: files('3270-ccw.c'))
> > +s390x_ss.add(when: 'CONFIG_LINUX', if_true: files('s390-pci-vfio.c'))

I think we need s/CONFIG_LINUX/CONFIG_VFIO/ here.

> >  
> >  virtio_ss = ss.source_set()
> >  virtio_ss.add(files('virtio-ccw.c'))
> > diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
> > new file mode 100644
> > index 000000000000..cb3f4d98adf8
> > --- /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 "hw/s390x/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;
> > +
> > +    assert(avail);
> > +
> > +    argsz = sizeof(struct vfio_iommu_type1_info);
> > +    info = g_malloc0(argsz);
> > +
> > +    /*
> > +     * If the specified argsz is not large enough to contain all capabilities
> > +     * it will be updated upon return from the ioctl.  Retry until we have
> > +     * a big enough buffer to hold the entire capability chain.
> > +     */
> > +retry:
> > +    info->argsz = argsz;
> > +
> > +    if (ioctl(fd, VFIO_IOMMU_GET_INFO, info)) {
> > +        return false;
> > +    }
> > +
> > +    if (info->argsz > argsz) {
> > +        argsz = info->argsz;
> > +        info = g_realloc(info, argsz);
> > +        goto retry;
> > +    }
> > +
> > +    /* If the capability exists, update with the current value */
> > +    return vfio_get_info_dma_avail(info, avail);
> > +}  
> 
> --without-default-devices configuration is broken, bisected
> to this commit:

Hm. Is this run in any of the CI tests? I did not even realize it
existed :)

> 
> hw/s390x/s390-pci-vfio.c:52: undefined reference to
> `vfio_get_info_dma_avail'
> 
> Can you have a look please?
> 
> Thanks.
>
Philippe Mathieu-Daudé Nov. 3, 2020, 10:57 a.m. UTC | #3
On 11/3/20 11:45 AM, Cornelia Huck wrote:
> On Tue, 3 Nov 2020 06:49:13 +0100
> Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> 
>> Hi Matthew,
>>
>> On 11/1/20 10:02 PM, Alex Williamson wrote:
>>> From: Matthew Rosato <mjrosato@linux.ibm.com>
>>>
>>> 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>
>>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>>> [aw: Fix non-Linux build with CONFIG_LINUX]
>>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
>>> ---
>>>  hw/s390x/meson.build             |    1 +
>>>  hw/s390x/s390-pci-vfio.c         |   54 ++++++++++++++++++++++++++++++++++++++
>>>  include/hw/s390x/s390-pci-vfio.h |   24 +++++++++++++++++
>>>  3 files changed, 79 insertions(+)
>>>  create mode 100644 hw/s390x/s390-pci-vfio.c
>>>  create mode 100644 include/hw/s390x/s390-pci-vfio.h
>>>
>>> diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
>>> index 948ceae7a7b3..f4663a835514 100644
>>> --- a/hw/s390x/meson.build
>>> +++ b/hw/s390x/meson.build
>>> @@ -27,6 +27,7 @@ s390x_ss.add(when: 'CONFIG_KVM', if_true: files(
>>>  ))
>>>  s390x_ss.add(when: 'CONFIG_S390_CCW_VIRTIO', if_true: files('s390-virtio-ccw.c'))
>>>  s390x_ss.add(when: 'CONFIG_TERMINAL3270', if_true: files('3270-ccw.c'))
>>> +s390x_ss.add(when: 'CONFIG_LINUX', if_true: files('s390-pci-vfio.c'))
> 
> I think we need s/CONFIG_LINUX/CONFIG_VFIO/ here.
> 
>>>  
>>>  virtio_ss = ss.source_set()
>>>  virtio_ss.add(files('virtio-ccw.c'))
>>> diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
>>> new file mode 100644
>>> index 000000000000..cb3f4d98adf8
>>> --- /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 "hw/s390x/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;
>>> +
>>> +    assert(avail);
>>> +
>>> +    argsz = sizeof(struct vfio_iommu_type1_info);
>>> +    info = g_malloc0(argsz);
>>> +
>>> +    /*
>>> +     * If the specified argsz is not large enough to contain all capabilities
>>> +     * it will be updated upon return from the ioctl.  Retry until we have
>>> +     * a big enough buffer to hold the entire capability chain.
>>> +     */
>>> +retry:
>>> +    info->argsz = argsz;
>>> +
>>> +    if (ioctl(fd, VFIO_IOMMU_GET_INFO, info)) {
>>> +        return false;
>>> +    }
>>> +
>>> +    if (info->argsz > argsz) {
>>> +        argsz = info->argsz;
>>> +        info = g_realloc(info, argsz);
>>> +        goto retry;
>>> +    }
>>> +
>>> +    /* If the capability exists, update with the current value */
>>> +    return vfio_get_info_dma_avail(info, avail);
>>> +}  
>>
>> --without-default-devices configuration is broken, bisected
>> to this commit:
> 
> Hm. Is this run in any of the CI tests? I did not even realize it
> existed :)

Paolo added it to Travis-CI 22 months ago:

commit 20885b5b1697247038018f3a7dfe8a84adf1b8e9
Author: Paolo Bonzini <pbonzini@redhat.com>
Date:   Thu Jan 31 15:57:53 2019 +0100

    .travis.yml: test that no-default-device builds do not regress

    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/.travis.yml b/.travis.yml
index cca57f43148..e942175dd30 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -149,6 +149,12 @@ matrix:
         - ${SRC_DIR}/scripts/travis/coverage-summary.sh


+    # We manually include builds which we disable "make check" for
+    - env:
+        - CONFIG="--without-default-devices"
+        - TEST_CMD=""
+
+
     # We manually include builds which we disable "make check" for
     - env:
         - CONFIG="--enable-debug --enable-tcg-interpreter"
---

> 
>>
>> hw/s390x/s390-pci-vfio.c:52: undefined reference to
>> `vfio_get_info_dma_avail'
>>
>> Can you have a look please?
>>
>> Thanks.
>>
>
Philippe Mathieu-Daudé Nov. 3, 2020, 11:08 a.m. UTC | #4
On 11/3/20 11:45 AM, Cornelia Huck wrote:
> On Tue, 3 Nov 2020 06:49:13 +0100
> Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> 
>> Hi Matthew,
>>
>> On 11/1/20 10:02 PM, Alex Williamson wrote:
>>> From: Matthew Rosato <mjrosato@linux.ibm.com>
>>>
>>> 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>
>>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>>> [aw: Fix non-Linux build with CONFIG_LINUX]
>>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
>>> ---
>>>  hw/s390x/meson.build             |    1 +
>>>  hw/s390x/s390-pci-vfio.c         |   54 ++++++++++++++++++++++++++++++++++++++
>>>  include/hw/s390x/s390-pci-vfio.h |   24 +++++++++++++++++
>>>  3 files changed, 79 insertions(+)
>>>  create mode 100644 hw/s390x/s390-pci-vfio.c
>>>  create mode 100644 include/hw/s390x/s390-pci-vfio.h
>>>
>>> diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
>>> index 948ceae7a7b3..f4663a835514 100644
>>> --- a/hw/s390x/meson.build
>>> +++ b/hw/s390x/meson.build
>>> @@ -27,6 +27,7 @@ s390x_ss.add(when: 'CONFIG_KVM', if_true: files(
>>>  ))
>>>  s390x_ss.add(when: 'CONFIG_S390_CCW_VIRTIO', if_true: files('s390-virtio-ccw.c'))
>>>  s390x_ss.add(when: 'CONFIG_TERMINAL3270', if_true: files('3270-ccw.c'))
>>> +s390x_ss.add(when: 'CONFIG_LINUX', if_true: files('s390-pci-vfio.c'))
> 
> I think we need s/CONFIG_LINUX/CONFIG_VFIO/ here.

With your change:

hw/s390x/s390-pci-bus.c:1079: undefined reference to
`s390_pci_end_dma_count'
hw/s390x/s390-pci-bus.c:1019: undefined reference to
`s390_pci_start_dma_count'
hw/s390x/s390-pci-bus.c:1021: undefined reference to `s390_pci_get_clp_info'

Do we need stubs instead?
Cornelia Huck Nov. 3, 2020, 11:15 a.m. UTC | #5
On Tue, 3 Nov 2020 12:08:20 +0100
Philippe Mathieu-Daudé <philmd@redhat.com> wrote:

> On 11/3/20 11:45 AM, Cornelia Huck wrote:
> > On Tue, 3 Nov 2020 06:49:13 +0100
> > Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> >   
> >> Hi Matthew,
> >>
> >> On 11/1/20 10:02 PM, Alex Williamson wrote:  
> >>> From: Matthew Rosato <mjrosato@linux.ibm.com>
> >>>
> >>> 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>
> >>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> >>> [aw: Fix non-Linux build with CONFIG_LINUX]
> >>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> >>> ---
> >>>  hw/s390x/meson.build             |    1 +
> >>>  hw/s390x/s390-pci-vfio.c         |   54 ++++++++++++++++++++++++++++++++++++++
> >>>  include/hw/s390x/s390-pci-vfio.h |   24 +++++++++++++++++
> >>>  3 files changed, 79 insertions(+)
> >>>  create mode 100644 hw/s390x/s390-pci-vfio.c
> >>>  create mode 100644 include/hw/s390x/s390-pci-vfio.h
> >>>
> >>> diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
> >>> index 948ceae7a7b3..f4663a835514 100644
> >>> --- a/hw/s390x/meson.build
> >>> +++ b/hw/s390x/meson.build
> >>> @@ -27,6 +27,7 @@ s390x_ss.add(when: 'CONFIG_KVM', if_true: files(
> >>>  ))
> >>>  s390x_ss.add(when: 'CONFIG_S390_CCW_VIRTIO', if_true: files('s390-virtio-ccw.c'))
> >>>  s390x_ss.add(when: 'CONFIG_TERMINAL3270', if_true: files('3270-ccw.c'))
> >>> +s390x_ss.add(when: 'CONFIG_LINUX', if_true: files('s390-pci-vfio.c'))  
> > 
> > I think we need s/CONFIG_LINUX/CONFIG_VFIO/ here.  
> 
> With your change:
> 
> hw/s390x/s390-pci-bus.c:1079: undefined reference to
> `s390_pci_end_dma_count'
> hw/s390x/s390-pci-bus.c:1019: undefined reference to
> `s390_pci_start_dma_count'
> hw/s390x/s390-pci-bus.c:1021: undefined reference to `s390_pci_get_clp_info'
> 
> Do we need stubs instead?
> 

We do have stubs; we just need them to be ifdeffed with CONFIG_VFIO
instead of CONFIG_LINUX. Currently preparing a proper patch.
diff mbox series

Patch

diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
index 948ceae7a7b3..f4663a835514 100644
--- a/hw/s390x/meson.build
+++ b/hw/s390x/meson.build
@@ -27,6 +27,7 @@  s390x_ss.add(when: 'CONFIG_KVM', if_true: files(
 ))
 s390x_ss.add(when: 'CONFIG_S390_CCW_VIRTIO', if_true: files('s390-virtio-ccw.c'))
 s390x_ss.add(when: 'CONFIG_TERMINAL3270', if_true: files('3270-ccw.c'))
+s390x_ss.add(when: 'CONFIG_LINUX', if_true: files('s390-pci-vfio.c'))
 
 virtio_ss = ss.source_set()
 virtio_ss.add(files('virtio-ccw.c'))
diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
new file mode 100644
index 000000000000..cb3f4d98adf8
--- /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 "hw/s390x/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;
+
+    assert(avail);
+
+    argsz = sizeof(struct vfio_iommu_type1_info);
+    info = g_malloc0(argsz);
+
+    /*
+     * If the specified argsz is not large enough to contain all capabilities
+     * it will be updated upon return from the ioctl.  Retry until we have
+     * a big enough buffer to hold the entire capability chain.
+     */
+retry:
+    info->argsz = argsz;
+
+    if (ioctl(fd, VFIO_IOMMU_GET_INFO, info)) {
+        return false;
+    }
+
+    if (info->argsz > argsz) {
+        argsz = info->argsz;
+        info = g_realloc(info, argsz);
+        goto retry;
+    }
+
+    /* If the capability exists, update with the current value */
+    return vfio_get_info_dma_avail(info, avail);
+}
+
diff --git a/include/hw/s390x/s390-pci-vfio.h b/include/hw/s390x/s390-pci-vfio.h
new file mode 100644
index 000000000000..1727292e9b5d
--- /dev/null
+++ b/include/hw/s390x/s390-pci-vfio.h
@@ -0,0 +1,24 @@ 
+/*
+ * 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.
+ */
+
+#ifndef HW_S390_PCI_VFIO_H
+#define HW_S390_PCI_VFIO_H
+
+#ifdef CONFIG_LINUX
+bool s390_pci_update_dma_avail(int fd, unsigned int *avail);
+#else
+static inline bool s390_pci_update_dma_avail(int fd, unsigned int *avail)
+{
+    return false;
+}
+#endif
+
+#endif