Re: [RFC PATCH 2/4] vfio: Implement a common device info helper

[Cédric Le Goater]

On 5/19/23 23:57, Alex Williamson wrote:

A common helper implementing the realloc algorithm for handling
capabilities.

Signed-off-by: Alex Williamson <alex.william...@redhat.com>

Reviewed-by: Cédric Le Goater <c...@redhat.com>

This is a good independent clean up that could be merged now.

Thanks,

C.

---
  hw/s390x/s390-pci-vfio.c      | 37 ++++------------------------
  hw/vfio/common.c              | 46 ++++++++++++++++++++++++++---------
  include/hw/vfio/vfio-common.h |  1 +
  3 files changed, 41 insertions(+), 43 deletions(-)

diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
index f51190d4662f..66e8ec3bdef9 100644
--- a/hw/s390x/s390-pci-vfio.c
+++ b/hw/s390x/s390-pci-vfio.c
@@ -289,38 +289,11 @@ static void s390_pci_read_pfip(S390PCIBusDevice *pbdev,
      memcpy(pbdev->zpci_fn.pfip, cap->pfip, CLP_PFIP_NR_SEGMENTS);
  }

-static struct vfio_device_info *get_device_info(S390PCIBusDevice *pbdev,

-                                                uint32_t argsz)
+static struct vfio_device_info *get_device_info(S390PCIBusDevice *pbdev);
  {
-    struct vfio_device_info *info = g_malloc0(argsz);
-    VFIOPCIDevice *vfio_pci;
-    int fd;
+    VFIOPCIDevice *vfio_pci = container_of(pbdev->pdev, VFIOPCIDevice, pdev);

- vfio_pci = container_of(pbdev->pdev, VFIOPCIDevice, pdev);

-    fd = vfio_pci->vbasedev.fd;
-
-    /*
-     * 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.  On error,
-     * just exit and rely on CLP defaults.
-     */
-retry:
-    info->argsz = argsz;
-
-    if (ioctl(fd, VFIO_DEVICE_GET_INFO, info)) {
-        trace_s390_pci_clp_dev_info(vfio_pci->vbasedev.name);
-        g_free(info);
-        return NULL;
-    }
-
-    if (info->argsz > argsz) {
-        argsz = info->argsz;
-        info = g_realloc(info, argsz);
-        goto retry;
-    }
-
-    return info;
+    return vfio_get_device_info(vfio_pci->vbasedev.fd);
  }

/*

@@ -335,7 +308,7 @@ bool s390_pci_get_host_fh(S390PCIBusDevice *pbdev, uint32_t 
*fh)

assert(fh); - info = get_device_info(pbdev, sizeof(*info));

+    info = get_device_info(pbdev);
      if (!info) {
          return false;
      }
@@ -356,7 +329,7 @@ void s390_pci_get_clp_info(S390PCIBusDevice *pbdev)
  {
      g_autofree struct vfio_device_info *info = NULL;

- info = get_device_info(pbdev, sizeof(*info));

+    info = get_device_info(pbdev);
      if (!info) {
          return;
      }
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 78358ede2764..ed142296e9fe 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -2843,11 +2843,35 @@ void vfio_put_group(VFIOGroup *group)
      }
  }

+struct vfio_device_info *vfio_get_device_info(int fd)

+{
+    struct vfio_device_info *info;
+    uint32_t argsz = sizeof(*info);
+
+    info = g_malloc0(argsz);
+
+retry:
+    info->argsz = argsz;
+
+    if (ioctl(fd, VFIO_DEVICE_GET_INFO, info)) {
+        g_free(info);
+        return NULL;
+    }
+
+    if (info->argsz > argsz) {
+        argsz = info->argsz;
+        info = g_realloc(info, argsz);
+        goto retry;
+    }
+
+    return info;
+}
+
  int vfio_get_device(VFIOGroup *group, const char *name,
                      VFIODevice *vbasedev, Error **errp)
  {
-    struct vfio_device_info dev_info = { .argsz = sizeof(dev_info) };
-    int ret, fd;
+    g_autofree struct vfio_device_info *info = NULL;
+    int fd;

fd = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);

      if (fd < 0) {
@@ -2859,11 +2883,11 @@ int vfio_get_device(VFIOGroup *group, const char *name,
          return fd;
      }

- ret = ioctl(fd, VFIO_DEVICE_GET_INFO, &dev_info);

-    if (ret) {
+    info = vfio_get_device_info(fd);
+    if (!info) {
          error_setg_errno(errp, errno, "error getting device info");
          close(fd);
-        return ret;
+        return -1;
      }

/*

@@ -2891,14 +2915,14 @@ int vfio_get_device(VFIOGroup *group, const char *name,
      vbasedev->group = group;
      QLIST_INSERT_HEAD(&group->device_list, vbasedev, next);

- vbasedev->num_irqs = dev_info.num_irqs;

-    vbasedev->num_regions = dev_info.num_regions;
-    vbasedev->flags = dev_info.flags;
+    vbasedev->num_irqs = info->num_irqs;
+    vbasedev->num_regions = info->num_regions;
+    vbasedev->flags = info->flags;
+
+    trace_vfio_get_device(name, info->flags, info->num_regions, 
info->num_irqs);

- trace_vfio_get_device(name, dev_info.flags, dev_info.num_regions,

-                          dev_info.num_irqs);
+    vbasedev->reset_works = !!(info->flags & VFIO_DEVICE_FLAGS_RESET);

- vbasedev->reset_works = !!(dev_info.flags & VFIO_DEVICE_FLAGS_RESET);

      return 0;
  }

diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h

index eed244f25f34..a8dcda592c08 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -212,6 +212,7 @@ void vfio_region_finalize(VFIORegion *region);
  void vfio_reset_handler(void *opaque);
  VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp);
  void vfio_put_group(VFIOGroup *group);
+struct vfio_device_info *vfio_get_device_info(int fd);
  int vfio_get_device(VFIOGroup *group, const char *name,
                      VFIODevice *vbasedev, Error **errp);