[PATCH v4 4/5] s390x/pci: Add routine to get the vfio dma available count

[Matthew Rosato <mjrosato@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
---
 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/meson.build b/hw/s390x/meson.build
index b63782d..ed2f66b 100644
--- a/hw/s390x/meson.build
+++ b/hw/s390x/meson.build
@@ -10,6 +10,7 @@ s390x_ss.add(files(
   's390-ccw.c',
   's390-pci-bus.c',
   's390-pci-inst.c',
+  's390-pci-vfio.c',
   's390-skeys.c',
   's390-stattrib.c',
   's390-virtio-hcall.c',
diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
new file mode 100644
index 0000000..f86654d
--- /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@xxxxxxxxxxxxx>
+ *
+ * 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;
+
+    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/hw/s390x/s390-pci-vfio.h b/hw/s390x/s390-pci-vfio.h
new file mode 100644
index 0000000..2a5a261
--- /dev/null
+++ b/hw/s390x/s390-pci-vfio.h
@@ -0,0 +1,17 @@
+/*
+ * s390 vfio-pci interfaces
+ *
+ * Copyright 2020 IBM Corp.
+ * Author(s): Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
+ *
+ * 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
+
+bool s390_pci_update_dma_avail(int fd, unsigned int *avail);
+
+#endif
-- 
1.8.3.1