On 4/9/25 15:48, John Levon wrote:
For vfio-user, device operations such as IRQ handling and region
read/writes are implemented in userspace over the control socket, not
ioctl() or read()/write() to the vfio kernel driver; add an ops vector
to generalize this, and implement vfio_device_io_ops_ioctl for
interacting with the kernel vfio driver.

Originally-by: John Johnson <john.g.john...@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimts...@oracle.com>
Signed-off-by: Jagannathan Raman <jag.ra...@oracle.com>
Signed-off-by: John Levon <john.le...@nutanix.com>
---
  hw/vfio/ap.c                  |   2 +-
  hw/vfio/ccw.c                 |   2 +-
  hw/vfio/container-base.c      |   6 +-
  hw/vfio/device.c              | 102 ++++++++++++++++++++++++++++++----
  hw/vfio/listener.c            |  13 +++--
  hw/vfio/pci.c                 |  40 +++++++------
  hw/vfio/platform.c            |   2 +-
  hw/vfio/region.c              |  17 ++++--
  include/hw/vfio/vfio-device.h |  24 +++++++-
  9 files changed, 155 insertions(+), 53 deletions(-)

diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
index f311bca5b6..b6233b2107 100644
--- a/hw/vfio/ap.c
+++ b/hw/vfio/ap.c
@@ -229,7 +229,7 @@ static void vfio_ap_instance_init(Object *obj)
       * handle ram_block_discard_disable().
       */
      vfio_device_init(vbasedev, VFIO_DEVICE_TYPE_AP, &vfio_ap_ops,
-                     DEVICE(vapdev), true);
+                     &vfio_device_io_ops_ioctl, DEVICE(vapdev), true);


We only have one io_ops implementation currently. Please drop all
the vfio_device_init() changes and keep vfio_device_io_ops_ioctl
static.

/* AP device is mdev type device */
      vbasedev->mdev = true;
diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
index 14dee7cd19..aee52b5a8d 100644
--- a/hw/vfio/ccw.c
+++ b/hw/vfio/ccw.c
@@ -676,7 +676,7 @@ static void vfio_ccw_instance_init(Object *obj)
       * ram_block_discard_disable().
       */
      vfio_device_init(vbasedev, VFIO_DEVICE_TYPE_CCW, &vfio_ccw_ops,
-                     DEVICE(vcdev), true);
+                     &vfio_device_io_ops_ioctl, DEVICE(vcdev), true);
  }
#ifdef CONFIG_IOMMUFD
diff --git a/hw/vfio/container-base.c b/hw/vfio/container-base.c
index 613fe1a00d..16fe5f79d2 100644
--- a/hw/vfio/container-base.c
+++ b/hw/vfio/container-base.c
@@ -198,11 +198,7 @@ static int vfio_device_dma_logging_report(VFIODevice 
*vbasedev, hwaddr iova,
      feature->flags = VFIO_DEVICE_FEATURE_GET |
                       VFIO_DEVICE_FEATURE_DMA_LOGGING_REPORT;
- if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
-        return -errno;
-    }
-
-    return 0;
+    return vbasedev->io_ops->device_feature(vbasedev, feature);
  }
static int vfio_container_iommu_query_dirty_bitmap(const VFIOContainerBase *bcontainer,
diff --git a/hw/vfio/device.c b/hw/vfio/device.c
index 102fa5a9b4..545d9f1faf 100644
--- a/hw/vfio/device.c
+++ b/hw/vfio/device.c
@@ -82,7 +82,7 @@ void vfio_device_irq_disable(VFIODevice *vbasedev, int index)
          .count = 0,
      };
- ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, &irq_set);
+    vbasedev->io_ops->set_irqs(vbasedev, &irq_set);
  }
void vfio_device_irq_unmask(VFIODevice *vbasedev, int index)
@@ -95,7 +95,7 @@ void vfio_device_irq_unmask(VFIODevice *vbasedev, int index)
          .count = 1,
      };
- ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, &irq_set);
+    vbasedev->io_ops->set_irqs(vbasedev, &irq_set);
  }
void vfio_device_irq_mask(VFIODevice *vbasedev, int index)
@@ -108,7 +108,7 @@ void vfio_device_irq_mask(VFIODevice *vbasedev, int index)
          .count = 1,
      };
- ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, &irq_set);
+    vbasedev->io_ops->set_irqs(vbasedev, &irq_set);
  }
static inline const char *action_to_str(int action)
@@ -155,6 +155,7 @@ bool vfio_device_irq_set_signaling(VFIODevice *vbasedev, 
int index, int subindex
      int argsz;
      const char *name;
      int32_t *pfd;
+    int ret;
argsz = sizeof(*irq_set) + sizeof(*pfd); @@ -167,7 +168,9 @@ bool vfio_device_irq_set_signaling(VFIODevice *vbasedev, int index, int subindex
      pfd = (int32_t *)&irq_set->data;
      *pfd = fd;
- if (!ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, irq_set)) {
+    ret = vbasedev->io_ops->set_irqs(vbasedev, irq_set);
+
+    if (!ret) {
          return true;
      }
@@ -188,22 +191,19 @@ bool vfio_device_irq_set_signaling(VFIODevice *vbasedev, int index, int subindex
  int vfio_device_get_irq_info(VFIODevice *vbasedev, int index,
                               struct vfio_irq_info *info)
  {
-    int ret;
-
      memset(info, 0, sizeof(*info));
info->argsz = sizeof(*info);
      info->index = index;
- ret = ioctl(vbasedev->fd, VFIO_DEVICE_GET_IRQ_INFO, info);
-
-    return ret < 0 ? -errno : ret;
+    return vbasedev->io_ops->get_irq_info(vbasedev, info);
  }
int vfio_device_get_region_info(VFIODevice *vbasedev, int index,
                                  struct vfio_region_info **info)
  {
      size_t argsz = sizeof(struct vfio_region_info);
+    int ret;
/* create region info cache */
      if (vbasedev->reginfo == NULL) {
@@ -222,10 +222,11 @@ int vfio_device_get_region_info(VFIODevice *vbasedev, int 
index,
  retry:
      (*info)->argsz = argsz;
- if (ioctl(vbasedev->fd, VFIO_DEVICE_GET_REGION_INFO, *info)) {
+    ret = vbasedev->io_ops->get_region_info(vbasedev, *info);
+    if (ret != 0) {
          g_free(*info);
          *info = NULL;
-        return -errno;
+        return ret;
      }
if ((*info)->argsz > argsz) {
@@ -332,10 +333,12 @@ void vfio_device_set_fd(VFIODevice *vbasedev, const char 
*str, Error **errp)
  }
void vfio_device_init(VFIODevice *vbasedev, int type, VFIODeviceOps *ops,
-                      DeviceState *dev, bool ram_discard)
+                      VFIODeviceIOOps *io_ops, DeviceState *dev,
+                      bool ram_discard)
  {
      vbasedev->type = type;
      vbasedev->ops = ops;
+    vbasedev->io_ops = io_ops;
      vbasedev->dev = dev;
      vbasedev->fd = -1;
@@ -463,3 +466,78 @@ void vfio_device_prepare(VFIODevice *vbasedev, VFIOContainerBase *bcontainer, vfio_device_get_all_region_info(vbasedev);
  }
+
+/*
+ * Traditional ioctl() based io
+ */
+
+static int vfio_device_io_device_feature(VFIODevice *vbasedev,
+                                         struct vfio_device_feature *feature)
+{
+    int ret;
+
+    ret = ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature);
+
+    return ret < 0 ? -errno : ret;
+}
+
+static int vfio_device_io_get_region_info(VFIODevice *vbasedev,
+                                          struct vfio_region_info *info)
+{
+    int ret;
+
+    ret = ioctl(vbasedev->fd, VFIO_DEVICE_GET_REGION_INFO, info);
+
+    return ret < 0 ? -errno : ret;
+}
+
+static int vfio_device_io_get_irq_info(VFIODevice *vbasedev,
+                                       struct vfio_irq_info *info)
+{
+    int ret;
+
+    ret = ioctl(vbasedev->fd, VFIO_DEVICE_GET_IRQ_INFO, info);
+
+    return ret < 0 ? -errno : ret;
+}
+
+static int vfio_device_io_set_irqs(VFIODevice *vbasedev,
+                                   struct vfio_irq_set *irqs)
+{
+    int ret;
+
+    ret = ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, irqs);
+
+    return ret < 0 ? -errno : ret;
+}
+
+static int vfio_device_io_region_read(VFIODevice *vbasedev, uint8_t index,
+                                      off_t off, uint32_t size, void *data)
+{
+    struct vfio_region_info *info = vbasedev->reginfo[index];
+    int ret;
+
+    ret = pread(vbasedev->fd, data, size, info->offset + off);
+
+    return ret < 0 ? -errno : ret;
+}
+
+static int vfio_device_io_region_write(VFIODevice *vbasedev, uint8_t index,
+                                       off_t off, uint32_t size, void *data)
+{
+    struct vfio_region_info *info = vbasedev->reginfo[index];
+    int ret;
+
+    ret = pwrite(vbasedev->fd, data, size, info->offset + off);
+
+    return ret < 0 ? -errno : ret;
+}
+
+VFIODeviceIOOps vfio_device_io_ops_ioctl = {
+    .device_feature = vfio_device_io_device_feature,
+    .get_region_info = vfio_device_io_get_region_info,
+    .get_irq_info = vfio_device_io_get_irq_info,
+    .set_irqs = vfio_device_io_set_irqs,
+    .region_read = vfio_device_io_region_read,
+    .region_write = vfio_device_io_region_write,
+};
diff --git a/hw/vfio/listener.c b/hw/vfio/listener.c
index bcf2b98e79..7ea9e0dfb7 100644
--- a/hw/vfio/listener.c
+++ b/hw/vfio/listener.c
@@ -821,13 +821,17 @@ static void 
vfio_devices_dma_logging_stop(VFIOContainerBase *bcontainer)
                       VFIO_DEVICE_FEATURE_DMA_LOGGING_STOP;
QLIST_FOREACH(vbasedev, &bcontainer->device_list, container_next) {
+        int ret;
+
          if (!vbasedev->dirty_tracking) {
              continue;
          }
- if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
+        ret = vbasedev->io_ops->device_feature(vbasedev, feature);
+
+        if (ret != 0) {
              warn_report("%s: Failed to stop DMA logging, err %d (%s)",
-                        vbasedev->name, -errno, strerror(errno));
+                        vbasedev->name, -ret, strerror(-ret));
          }
          vbasedev->dirty_tracking = false;
      }
@@ -928,10 +932,9 @@ static bool 
vfio_devices_dma_logging_start(VFIOContainerBase *bcontainer,
              continue;
          }
- ret = ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature);
+        ret = vbasedev->io_ops->device_feature(vbasedev, feature);
          if (ret) {
-            ret = -errno;
-            error_setg_errno(errp, errno, "%s: Failed to start DMA logging",
+            error_setg_errno(errp, -ret, "%s: Failed to start DMA logging",
                               vbasedev->name);
              goto out;
          }
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index b40d5abdfd..ff2b15ff02 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -381,7 +381,7 @@ static void vfio_msi_interrupt(void *opaque)
  static int vfio_enable_msix_no_vec(VFIOPCIDevice *vdev)
  {
      g_autofree struct vfio_irq_set *irq_set = NULL;
-    int ret = 0, argsz;
+    int argsz;
      int32_t *fd;
argsz = sizeof(*irq_set) + sizeof(*fd);
@@ -396,9 +396,7 @@ static int vfio_enable_msix_no_vec(VFIOPCIDevice *vdev)
      fd = (int32_t *)&irq_set->data;
      *fd = -1;
- ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_SET_IRQS, irq_set);
-
-    return ret < 0 ? -errno : ret;
+    return vdev->vbasedev.io_ops->set_irqs(&vdev->vbasedev, irq_set);
  }
static int vfio_enable_vectors(VFIOPCIDevice *vdev, bool msix)
@@ -455,11 +453,11 @@ static int vfio_enable_vectors(VFIOPCIDevice *vdev, bool 
msix)
          fds[i] = fd;
      }
- ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_SET_IRQS, irq_set);
+    ret = vdev->vbasedev.io_ops->set_irqs(&vdev->vbasedev, irq_set);
g_free(irq_set); - return ret < 0 ? -errno : ret;
+    return ret;
  }
static void vfio_add_kvm_msi_virq(VFIOPCIDevice *vdev, VFIOMSIVector *vector,
@@ -917,18 +915,22 @@ static void vfio_pci_load_rom(VFIOPCIDevice *vdev)
      memset(vdev->rom, 0xff, size);
while (size) {
-        bytes = pread(vbasedev->fd, vdev->rom + off,
-                      size, vdev->rom_offset + off);
+        bytes = vbasedev->io_ops->region_read(vbasedev,
+                                              VFIO_PCI_ROM_REGION_INDEX,
+                                              off, size, vdev->rom + off);
+
          if (bytes == 0) {
              break;
          } else if (bytes > 0) {
              off += bytes;
              size -= bytes;
          } else {
-            if (errno == EINTR || errno == EAGAIN) {
+            if (bytes == -EINTR || bytes == -EAGAIN) {
                  continue;
              }
-            error_report("vfio: Error reading device ROM: %m");
+            error_report("vfio: Error reading device ROM: %s",
+                         strerror(-bytes));
+
              break;
          }
      }
@@ -968,22 +970,18 @@ static void vfio_pci_load_rom(VFIOPCIDevice *vdev)
  static int vfio_pci_config_space_read(VFIOPCIDevice *vdev, off_t offset,
                                        uint32_t size, void *data)
  {
-    ssize_t ret;
-
-    ret = pread(vdev->vbasedev.fd, data, size, vdev->config_offset + offset);
-
-    return ret < 0 ? -errno : (int)ret;
+    return vdev->vbasedev.io_ops->region_read(&vdev->vbasedev,
+                                              VFIO_PCI_CONFIG_REGION_INDEX,
+                                              offset, size, data);
  }
/* "Raw" write of underlying config space. */
  static int vfio_pci_config_space_write(VFIOPCIDevice *vdev, off_t offset,
                                         uint32_t size, void *data)
  {
-    ssize_t ret;
-
-    ret = pwrite(vdev->vbasedev.fd, data, size, vdev->config_offset + offset);
-
-    return ret < 0 ? -errno : (int)ret;
+    return vdev->vbasedev.io_ops->region_write(&vdev->vbasedev,
+                                               VFIO_PCI_CONFIG_REGION_INDEX,
+                                               offset, size, data);
  }
static uint64_t vfio_rom_read(void *opaque, hwaddr addr, unsigned size)
@@ -3405,7 +3403,7 @@ static void vfio_instance_init(Object *obj)
      vdev->host.function = ~0U;
vfio_device_init(vbasedev, VFIO_DEVICE_TYPE_PCI, &vfio_pci_ops,
-                     DEVICE(vdev), false);
+                     &vfio_device_io_ops_ioctl, DEVICE(vdev), false);
vdev->nv_gpudirect_clique = 0xFF; diff --git a/hw/vfio/platform.c b/hw/vfio/platform.c
index fd176c18a4..28eedfa571 100644
--- a/hw/vfio/platform.c
+++ b/hw/vfio/platform.c
@@ -650,7 +650,7 @@ static void vfio_platform_instance_init(Object *obj)
      VFIODevice *vbasedev = &vdev->vbasedev;
vfio_device_init(vbasedev, VFIO_DEVICE_TYPE_PLATFORM, &vfio_platform_ops,
-                     DEVICE(vdev), false);
+                     &vfio_device_io_ops_ioctl, DEVICE(vdev), false);
  }
#ifdef CONFIG_IOMMUFD
diff --git a/hw/vfio/region.c b/hw/vfio/region.c
index ef2630cac3..35fb81c04a 100644
--- a/hw/vfio/region.c
+++ b/hw/vfio/region.c
@@ -45,6 +45,7 @@ void vfio_region_write(void *opaque, hwaddr addr,
          uint32_t dword;
          uint64_t qword;
      } buf;
+    int ret;
switch (size) {
      case 1:
@@ -64,11 +65,13 @@ void vfio_region_write(void *opaque, hwaddr addr,
          break;
      }
- if (pwrite(vbasedev->fd, &buf, size, region->fd_offset + addr) != size) {
+    ret = vbasedev->io_ops->region_write(vbasedev, region->nr,
+                                         addr, size, &buf);
+    if (ret != size) {
          error_report("%s(%s:region%d+0x%"HWADDR_PRIx", 0x%"PRIx64
-                     ",%d) failed: %m",
+                     ",%d) failed: %s",
                       __func__, vbasedev->name, region->nr,
-                     addr, data, size);
+                     addr, data, size, ret < 0 ? strerror(ret) : "short 
write");
      }
trace_vfio_region_write(vbasedev->name, region->nr, addr, data, size);
@@ -96,11 +99,13 @@ uint64_t vfio_region_read(void *opaque,
          uint64_t qword;
      } buf;
      uint64_t data = 0;
+    int ret;
- if (pread(vbasedev->fd, &buf, size, region->fd_offset + addr) != size) {
-        error_report("%s(%s:region%d+0x%"HWADDR_PRIx", %d) failed: %m",
+    ret = vbasedev->io_ops->region_read(vbasedev, region->nr, addr, size, 
&buf);
+    if (ret != size) {
+        error_report("%s(%s:region%d+0x%"HWADDR_PRIx", %d) failed: %s",
                       __func__, vbasedev->name, region->nr,
-                     addr, size);
+                     addr, size, ret < 0 ? strerror(ret) : "short read");
          return (uint64_t)-1;
      }
      switch (size) {
diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h
index 967b07cd89..cb2f581826 100644
--- a/include/hw/vfio/vfio-device.h
+++ b/include/hw/vfio/vfio-device.h
@@ -41,6 +41,7 @@ enum {
  };
typedef struct VFIODeviceOps VFIODeviceOps;
+typedef struct VFIODeviceIOOps VFIODeviceIOOps;
  typedef struct VFIOMigration VFIOMigration;
typedef struct IOMMUFDBackend IOMMUFDBackend;
@@ -66,6 +67,7 @@ typedef struct VFIODevice {
      OnOffAuto migration_multifd_transfer;
      bool migration_events;
      VFIODeviceOps *ops;
+    VFIODeviceIOOps *io_ops;
      unsigned int num_irqs;
      unsigned int num_regions;
      unsigned int flags;
@@ -140,6 +142,25 @@ typedef QLIST_HEAD(VFIODeviceList, VFIODevice) 
VFIODeviceList;
  extern VFIODeviceList vfio_device_list;
#ifdef CONFIG_LINUX
+/*
+ * How devices communicate with the server.  The default option is through
+ * ioctl() to the kernel VFIO driver, but vfio-user can use a socket to a 
remote
+ * process.
+ */
+struct VFIODeviceIOOps {
+    int (*device_feature)(VFIODevice *vdev, struct vfio_device_feature *);
+    int (*get_region_info)(VFIODevice *vdev,
+                           struct vfio_region_info *info);
+    int (*get_irq_info)(VFIODevice *vdev, struct vfio_irq_info *irq);
+    int (*set_irqs)(VFIODevice *vdev, struct vfio_irq_set *irqs);
+    int (*region_read)(VFIODevice *vdev, uint8_t nr, off_t off, uint32_t size,
+                       void *data);
+    int (*region_write)(VFIODevice *vdev, uint8_t nr, off_t off, uint32_t size,
+                        void *data);
+};


Could you please add documentation for this new struct.


Thanks,

C.




+extern VFIODeviceIOOps vfio_device_io_ops_ioctl;
+
  int vfio_device_get_region_info(VFIODevice *vbasedev, int index,
                                  struct vfio_region_info **info);
  int vfio_device_get_region_info_type(VFIODevice *vbasedev, uint32_t type,
@@ -154,6 +175,7 @@ int vfio_device_get_irq_info(VFIODevice *vbasedev, int 
index,
  bool vfio_device_get_name(VFIODevice *vbasedev, Error **errp);
  void vfio_device_set_fd(VFIODevice *vbasedev, const char *str, Error **errp);
  void vfio_device_init(VFIODevice *vbasedev, int type, VFIODeviceOps *ops,
-                      DeviceState *dev, bool ram_discard);
+                      VFIODeviceIOOps *io_ops, DeviceState *dev,
+                      bool ram_discard);
  int vfio_device_get_aw_bits(VFIODevice *vdev);
  #endif /* HW_VFIO_VFIO_COMMON_H */


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