On 2/19/25 15:48, John Levon wrote:
From: Jagannathan Raman <jag.ra...@oracle.com>

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_dev_io_ioctl for interacting
with the kernel vfio driver.

The ops consistently use the "-errno" return style, as the vfio-user
implementations get their errors from response messages not from the
kernel; adjust the callers to handle this as necessary.

Please adjust the callers before introducing the new ops.
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/common.c              |  13 +--
  hw/vfio/helpers.c             | 110 ++++++++++++++++++++++---
  hw/vfio/pci.c                 | 147 ++++++++++++++++++++++------------
  hw/vfio/platform.c            |   2 +-
  include/hw/vfio/vfio-common.h |  27 ++++++-
  7 files changed, 227 insertions(+), 76 deletions(-)

diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
index 30b08ad375..1adce1ab40 100644
--- a/hw/vfio/ap.c
+++ b/hw/vfio/ap.c
@@ -228,7 +228,7 @@ 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_dev_io_ioctl, DEVICE(vapdev), true);

Hmm, most of these parameters should be VFIODeviceClass attributes but
it doesn't exist. I don't see any nice improvements. Let's keep it.

/* AP device is mdev type device */
      vbasedev->mdev = true;
diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
index 22378d50bc..8c16648819 100644
--- a/hw/vfio/ccw.c
+++ b/hw/vfio/ccw.c
@@ -682,7 +682,7 @@ 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_dev_io_ioctl, DEVICE(vcdev), true);
  }
#ifdef CONFIG_IOMMUFD
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 1866b3d3c5..cc0c0f7fc7 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -971,7 +971,7 @@ static void vfio_devices_dma_logging_stop(VFIOContainerBase 
*bcontainer)
              continue;
          }
- if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
+        if (vbasedev->io->device_feature(vbasedev, feature)) {
              warn_report("%s: Failed to stop DMA logging, err %d (%s)",
                          vbasedev->name, -errno, strerror(errno));
          }
@@ -1074,10 +1074,9 @@ static bool 
vfio_devices_dma_logging_start(VFIOContainerBase *bcontainer,
              continue;
          }
- ret = ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature);
+        ret = vbasedev->io->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;
          }
@@ -1145,6 +1144,7 @@ static int vfio_device_dma_logging_report(VFIODevice 
*vbasedev, hwaddr iova,
      struct vfio_device_feature *feature = (struct vfio_device_feature *)buf;
      struct vfio_device_feature_dma_logging_report *report =
          (struct vfio_device_feature_dma_logging_report *)feature->data;
+    int ret;
report->iova = iova;
      report->length = size;
@@ -1155,8 +1155,9 @@ 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;
+    ret = vbasedev->io->device_feature(vbasedev, feature);
+    if (ret) {
+        return -ret;
      }
return 0;
diff --git a/hw/vfio/helpers.c b/hw/vfio/helpers.c
index 94bbc5747c..bef1540295 100644
--- a/hw/vfio/helpers.c
+++ b/hw/vfio/helpers.c
@@ -44,7 +44,7 @@ void vfio_disable_irqindex(VFIODevice *vbasedev, int index)
          .count = 0,
      };
- ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, &irq_set);
+    vbasedev->io->set_irqs(vbasedev, &irq_set);
  }
void vfio_unmask_single_irqindex(VFIODevice *vbasedev, int index)
@@ -57,7 +57,7 @@ void vfio_unmask_single_irqindex(VFIODevice *vbasedev, int 
index)
          .count = 1,
      };
- ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, &irq_set);
+    vbasedev->io->set_irqs(vbasedev, &irq_set);
  }
void vfio_mask_single_irqindex(VFIODevice *vbasedev, int index)
@@ -70,7 +70,7 @@ void vfio_mask_single_irqindex(VFIODevice *vbasedev, int 
index)
          .count = 1,
      };
- ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, &irq_set);
+    vbasedev->io->set_irqs(vbasedev, &irq_set);
  }
static inline const char *action_to_str(int action)
@@ -117,6 +117,7 @@ bool vfio_set_irq_signaling(VFIODevice *vbasedev, int 
index, int subindex,
      int argsz;
      const char *name;
      int32_t *pfd;
+    int ret;
argsz = sizeof(*irq_set) + sizeof(*pfd); @@ -129,7 +130,9 @@ bool vfio_set_irq_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->set_irqs(vbasedev, irq_set);
+
+    if (!ret) {
          return true;
      }
@@ -161,6 +164,7 @@ void vfio_region_write(void *opaque, hwaddr addr,
          uint32_t dword;
          uint64_t qword;
      } buf;
+    int ret;
switch (size) {
      case 1:
@@ -180,11 +184,12 @@ void vfio_region_write(void *opaque, hwaddr addr,
          break;
      }
- if (pwrite(vbasedev->fd, &buf, size, region->fd_offset + addr) != size) {
+    ret = vbasedev->io->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);
@@ -212,11 +217,13 @@ 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->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) {
@@ -561,6 +568,7 @@ int vfio_get_region_info(VFIODevice *vbasedev, int index,
                           struct vfio_region_info **info)
  {
      size_t argsz = sizeof(struct vfio_region_info);
+    int ret;
/* create region cache */
      if (vbasedev->regions == NULL) {
@@ -579,10 +587,11 @@ int vfio_get_region_info(VFIODevice *vbasedev, int index,
  retry:
      (*info)->argsz = argsz;
- if (ioctl(vbasedev->fd, VFIO_DEVICE_GET_REGION_INFO, *info)) {
+    ret = vbasedev->io->get_region_info(vbasedev, *info);
+    if (ret != 0) {
          g_free(*info);
          *info = NULL;
-        return -errno;
+        return ret;
      }
if ((*info)->argsz > argsz) {
@@ -689,11 +698,12 @@ 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)
+                      VFIODeviceIO *io, DeviceState *dev, bool ram_discard)
  {
      vbasedev->type = type;
      vbasedev->ops = ops;
      vbasedev->dev = dev;
+    vbasedev->io = io;
      vbasedev->fd = -1;
vbasedev->ram_block_discard_allowed = ram_discard;
@@ -749,3 +759,77 @@ VFIODevice *vfio_get_vfio_device(Object *obj)
          return NULL;
      }
  }
+
+/*
+ * Traditional ioctl() based io
+ */
+
+static int vfio_io_device_feature(VFIODevice *vbasedev,
+                                  struct vfio_device_feature *feature)

'vfio_device' prefix ? vfio_device_io_device_feature. Minor since it's
local to the file.

+{
+    int ret;
+
+    ret = ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature);
+
+    return ret < 0 ? -errno : ret;
+}
+
+static int vfio_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_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_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_io_region_read(VFIODevice *vbasedev, uint8_t index, off_t off,
+                               uint32_t size, void *data)
+{
+    struct vfio_region_info *info = vbasedev->regions[index];
+    int ret;
+
+    ret = pread(vbasedev->fd, data, size, info->offset + off);
+
+    return ret < 0 ? -errno : ret;
+}
+
+static int vfio_io_region_write(VFIODevice *vbasedev, uint8_t index, off_t off,
+                                uint32_t size, void *data)
+{
+    struct vfio_region_info *info = vbasedev->regions[index];
+    int ret;
+
+    ret = pwrite(vbasedev->fd, data, size, info->offset + off);
+
+    return ret < 0 ? -errno : ret;
+}
+
+VFIODeviceIO vfio_dev_io_ioctl = {

vfio_device_io_ops_ioctl

+    .device_feature = vfio_io_device_feature,
+    .get_region_info = vfio_io_get_region_info,
+    .get_irq_info = vfio_io_get_irq_info,
+    .set_irqs = vfio_io_set_irqs,
+    .region_read = vfio_io_region_read,
+    .region_write = vfio_io_region_write,
+};
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 812743e9dd..a9cc9366fb 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -45,6 +45,14 @@
  #include "migration/qemu-file.h"
  #include "system/iommufd.h"
+/* convenience macros for PCI config space */
+#define VDEV_CONFIG_READ(vbasedev, off, size, data) \
+    ((vbasedev)->io->region_read((vbasedev), VFIO_PCI_CONFIG_REGION_INDEX, \
+                                 (off), (size), (data)))
+#define VDEV_CONFIG_WRITE(vbasedev, off, size, data) \
+    ((vbasedev)->io->region_write((vbasedev), VFIO_PCI_CONFIG_REGION_INDEX, \
+                                  (off), (size), (data)))
+

Pease introduce these helpers in a separate patch.

  #define TYPE_VFIO_PCI_NOHOTPLUG "vfio-pci-nohotplug"
/* Protected by BQL */
@@ -379,6 +387,7 @@ 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;
+    VFIODevice *vbasedev = &vdev->vbasedev;
      int ret = 0, argsz;
      int32_t *fd;
@@ -394,7 +403,7 @@ 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);
+    ret = vbasedev->io->set_irqs(vbasedev, irq_set);
return ret;
  }
@@ -453,7 +462,7 @@ 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->set_irqs(&vdev->vbasedev, irq_set);
g_free(irq_set); @@ -763,7 +772,8 @@ retry:
      ret = vfio_enable_vectors(vdev, false);
      if (ret) {
          if (ret < 0) {
-            error_report("vfio: Error: Failed to setup MSI fds: %m");
+            error_report("vfio: Error: Failed to setup MSI fds: %s",
+                         strerror(-ret));
          } else {
              error_report("vfio: Error: Failed to enable %d "
                           "MSI vectors, retry with %d", vdev->nr_vectors, ret);
@@ -879,14 +889,17 @@ static void vfio_update_msi(VFIOPCIDevice *vdev)
static void vfio_pci_load_rom(VFIOPCIDevice *vdev)
  {
+    VFIODevice *vbasedev = &vdev->vbasedev;
      struct vfio_region_info *reg_info = NULL;
      uint64_t size;
      off_t off = 0;
      ssize_t bytes;
+    int ret;
- if (vfio_get_region_info(&vdev->vbasedev,
-                             VFIO_PCI_ROM_REGION_INDEX, &reg_info)) {
-        error_report("vfio: Error getting ROM info: %m");
+    ret = vfio_get_region_info(vbasedev, VFIO_PCI_ROM_REGION_INDEX, &reg_info);
+
+    if (ret != 0) {
+        error_report("vfio: Error getting ROM info: %s", strerror(-ret));
          return;
      }
@@ -911,18 +924,19 @@ static void vfio_pci_load_rom(VFIOPCIDevice *vdev)
      memset(vdev->rom, 0xff, size);
while (size) {
-        bytes = pread(vdev->vbasedev.fd, vdev->rom + off,
-                      size, vdev->rom_offset + off);
+        bytes = vbasedev->io->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;
          }
      }
@@ -1010,10 +1024,9 @@ static const MemoryRegionOps vfio_rom_ops = {
static void vfio_pci_size_rom(VFIOPCIDevice *vdev)
  {
+    VFIODevice *vbasedev = &vdev->vbasedev;
      uint32_t orig, size = cpu_to_le32((uint32_t)PCI_ROM_ADDRESS_MASK);
-    off_t offset = vdev->config_offset + PCI_ROM_ADDRESS;
      char *name;
-    int fd = vdev->vbasedev.fd;
if (vdev->pdev.romfile || !vdev->pdev.rom_bar) {
          /* Since pci handles romfile, just print a message and return */
@@ -1030,11 +1043,12 @@ static void vfio_pci_size_rom(VFIOPCIDevice *vdev)
       * Use the same size ROM BAR as the physical device.  The contents
       * will get filled in later when the guest tries to read it.
       */
-    if (pread(fd, &orig, 4, offset) != 4 ||
-        pwrite(fd, &size, 4, offset) != 4 ||
-        pread(fd, &size, 4, offset) != 4 ||
-        pwrite(fd, &orig, 4, offset) != 4) {
-        error_report("%s(%s) failed: %m", __func__, vdev->vbasedev.name);
+    if (VDEV_CONFIG_READ(vbasedev, PCI_ROM_ADDRESS, 4, &orig) != 4 ||
+        VDEV_CONFIG_WRITE(vbasedev, PCI_ROM_ADDRESS, 4, &size) != 4 ||
+        VDEV_CONFIG_READ(vbasedev, PCI_ROM_ADDRESS, 4, &size) != 4 ||
+        VDEV_CONFIG_WRITE(vbasedev, PCI_ROM_ADDRESS, 4, &orig) != 4) {
+
+        error_report("%s(%s) ROM access failed", __func__, vbasedev->name);
          return;
      }
@@ -1214,6 +1228,7 @@ static void vfio_sub_page_bar_update_mapping(PCIDevice *pdev, int bar)
  uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len)
  {
      VFIOPCIDevice *vdev = VFIO_PCI_BASE(pdev);
+    VFIODevice *vbasedev = &vdev->vbasedev;
      uint32_t emu_bits = 0, emu_val = 0, phys_val = 0, val;
memcpy(&emu_bits, vdev->emulated_config_bits + addr, len);
@@ -1226,12 +1241,13 @@ uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t 
addr, int len)
      if (~emu_bits & (0xffffffffU >> (32 - len * 8))) {
          ssize_t ret;
- ret = pread(vdev->vbasedev.fd, &phys_val, len,
-                    vdev->config_offset + addr);
+        ret = VDEV_CONFIG_READ(vbasedev, addr, len, &phys_val);
          if (ret != len) {
-            error_report("%s(%s, 0x%x, 0x%x) failed: %m",
-                         __func__, vdev->vbasedev.name, addr, len);
-            return -errno;
+            const char *err = ret < 0 ? strerror(-ret) : "short read";
+
+            error_report("%s(%s, 0x%x, 0x%x) failed: %s",
+                         __func__, vbasedev->name, addr, len, err);
+            return -1;
          }
          phys_val = le32_to_cpu(phys_val);
      }
@@ -1247,15 +1263,19 @@ void vfio_pci_write_config(PCIDevice *pdev,
                             uint32_t addr, uint32_t val, int len)
  {
      VFIOPCIDevice *vdev = VFIO_PCI_BASE(pdev);
+    VFIODevice *vbasedev = &vdev->vbasedev;
      uint32_t val_le = cpu_to_le32(val);
+    int ret;
trace_vfio_pci_write_config(vdev->vbasedev.name, addr, val, len); /* Write everything to VFIO, let it filter out what we can't write */
-    if (pwrite(vdev->vbasedev.fd, &val_le, len, vdev->config_offset + addr)
-                != len) {
-        error_report("%s(%s, 0x%x, 0x%x, 0x%x) failed: %m",
-                     __func__, vdev->vbasedev.name, addr, val, len);
+    ret = VDEV_CONFIG_WRITE(vbasedev, addr, len, &val_le);
+    if (ret != len) {
+        const char *err = ret < 0 ? strerror(-ret) : "short write";
+
+        error_report("%s(%s, 0x%x, 0x%x, 0x%x) failed: %s",
+                     __func__, vbasedev->name, addr, val, len, err);
      }
/* MSI/MSI-X Enabling/Disabling */
@@ -1343,9 +1363,12 @@ static bool vfio_msi_setup(VFIOPCIDevice *vdev, int pos, 
Error **errp)
      int ret, entries;
      Error *err = NULL;
- if (pread(vdev->vbasedev.fd, &ctrl, sizeof(ctrl),
-              vdev->config_offset + pos + PCI_CAP_FLAGS) != sizeof(ctrl)) {
-        error_setg_errno(errp, errno, "failed reading MSI PCI_CAP_FLAGS");
+    ret = VDEV_CONFIG_READ(&vdev->vbasedev, pos + PCI_CAP_FLAGS,
+                           sizeof(ctrl), &ctrl);
+    if (ret != sizeof(ctrl)) {
+        const char *errmsg = ret < 0 ? strerror(-ret) : "short read";
+
+        error_setg(errp, "failed reading MSI PCI_CAP_FLAGS %s", errmsg);
          return false;
      }
      ctrl = le16_to_cpu(ctrl);
@@ -1549,34 +1572,43 @@ static bool vfio_pci_relocate_msix(VFIOPCIDevice *vdev, 
Error **errp)
   */
  static bool vfio_msix_early_setup(VFIOPCIDevice *vdev, Error **errp)
  {
+    VFIODevice *vbasedev = &vdev->vbasedev;
      uint8_t pos;
      uint16_t ctrl;
      uint32_t table, pba;
-    int ret, fd = vdev->vbasedev.fd;
      struct vfio_irq_info irq_info = { .argsz = sizeof(irq_info),
                                        .index = VFIO_PCI_MSIX_IRQ_INDEX };
      VFIOMSIXInfo *msix;
+    int ret;
pos = pci_find_capability(&vdev->pdev, PCI_CAP_ID_MSIX);
      if (!pos) {
          return true;
      }
- if (pread(fd, &ctrl, sizeof(ctrl),
-              vdev->config_offset + pos + PCI_MSIX_FLAGS) != sizeof(ctrl)) {
-        error_setg_errno(errp, errno, "failed to read PCI MSIX FLAGS");
+    ret = VDEV_CONFIG_READ(vbasedev, pos + PCI_MSIX_FLAGS,
+                           sizeof(ctrl), &ctrl);
+    if (ret != sizeof(ctrl)) {
+        const char *err = ret < 0 ? strerror(-ret) : "short read";
+
+        error_setg(errp, "failed to read PCI MSIX FLAGS: %s", err);
          return false;
      }
- if (pread(fd, &table, sizeof(table),
-              vdev->config_offset + pos + PCI_MSIX_TABLE) != sizeof(table)) {
-        error_setg_errno(errp, errno, "failed to read PCI MSIX TABLE");
+    ret = VDEV_CONFIG_READ(vbasedev, pos + PCI_MSIX_TABLE,
+                           sizeof(table), &table);
+    if (ret != sizeof(table)) {
+        const char *err = ret < 0 ? strerror(-ret) : "short read";
+
+        error_setg(errp, "failed to read PCI MSIX TABLE: %s", err);
          return false;
      }
- if (pread(fd, &pba, sizeof(pba),
-              vdev->config_offset + pos + PCI_MSIX_PBA) != sizeof(pba)) {
-        error_setg_errno(errp, errno, "failed to read PCI MSIX PBA");
+    ret = VDEV_CONFIG_READ(vbasedev, pos + PCI_MSIX_PBA, sizeof(pba), &pba);
+    if (ret != sizeof(pba)) {
+        const char *err = ret < 0 ? strerror(-ret) : "short read";
+
+        error_setg(errp, "failed to read PCI MSIX PBA: %s", err);
          return false;
      }
@@ -1591,7 +1623,7 @@ static bool vfio_msix_early_setup(VFIOPCIDevice *vdev, Error **errp)
      msix->pba_offset = pba & ~PCI_MSIX_FLAGS_BIRMASK;
      msix->entries = (ctrl & PCI_MSIX_FLAGS_QSIZE) + 1;
- ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_GET_IRQ_INFO, &irq_info);
+    ret = vdev->vbasedev.io->get_irq_info(&vdev->vbasedev, &irq_info);
      if (ret < 0) {
          error_setg_errno(errp, -ret, "failed to get MSI-X irq info");
          g_free(msix);
@@ -1735,10 +1767,12 @@ static void vfio_bar_prepare(VFIOPCIDevice *vdev, int 
nr)
      }
/* Determine what type of BAR this is for registration */
-    ret = pread(vdev->vbasedev.fd, &pci_bar, sizeof(pci_bar),
-                vdev->config_offset + PCI_BASE_ADDRESS_0 + (4 * nr));
+    ret = VDEV_CONFIG_READ(&vdev->vbasedev, PCI_BASE_ADDRESS_0 + (4 * nr),
+                           sizeof(pci_bar), &pci_bar);
      if (ret != sizeof(pci_bar)) {
-        error_report("vfio: Failed to read BAR %d (%m)", nr);
+        const char *err =  ret < 0 ? strerror(-ret) : "short read";
+
+        error_report("vfio: Failed to read BAR %d: %s", nr, err);
          return;
      }
@@ -2438,21 +2472,25 @@ void vfio_pci_pre_reset(VFIOPCIDevice *vdev) void vfio_pci_post_reset(VFIOPCIDevice *vdev)
  {
+    VFIODevice *vbasedev = &vdev->vbasedev;
      Error *err = NULL;
-    int nr;
+    int ret, nr;
if (!vfio_intx_enable(vdev, &err)) {
          error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);
      }
for (nr = 0; nr < PCI_NUM_REGIONS - 1; ++nr) {
-        off_t addr = vdev->config_offset + PCI_BASE_ADDRESS_0 + (4 * nr);
+        off_t addr = PCI_BASE_ADDRESS_0 + (4 * nr);
          uint32_t val = 0;
          uint32_t len = sizeof(val);
- if (pwrite(vdev->vbasedev.fd, &val, len, addr) != len) {
-            error_report("%s(%s) reset bar %d failed: %m", __func__,
-                         vdev->vbasedev.name, nr);
+        ret = VDEV_CONFIG_WRITE(vbasedev, addr, len, &val);
+        if (ret != len) {
+            const char *errmsg = ret < 0 ? strerror(-ret) : "short write";
+
+            error_report("%s(%s) reset bar %d failed: %s", __func__,
+                         vbasedev->name, nr, errmsg);
          }
      }
@@ -2794,10 +2832,10 @@ static bool vfio_populate_device(VFIOPCIDevice *vdev, Error **errp) irq_info.index = VFIO_PCI_ERR_IRQ_INDEX; - ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_GET_IRQ_INFO, &irq_info);
+    ret = vbasedev->io->get_irq_info(vbasedev, &irq_info);
      if (ret) {
          /* This can fail for an old kernel or legacy PCI dev */
-        trace_vfio_populate_device_get_irq_info_failure(strerror(errno));
+        trace_vfio_populate_device_get_irq_info_failure(strerror(-ret));
      } else if (irq_info.count == 1) {
          vdev->pci_aer = true;
      } else {
@@ -2915,8 +2953,11 @@ static void vfio_register_req_notifier(VFIOPCIDevice 
*vdev)
          return;
      }
- if (ioctl(vdev->vbasedev.fd,
-              VFIO_DEVICE_GET_IRQ_INFO, &irq_info) < 0 || irq_info.count < 1) {
+    if (vdev->vbasedev.io->get_irq_info(&vdev->vbasedev, &irq_info) < 0) {
+        return;
+    }
+
+    if (irq_info.count < 1) {
          return;
      }
@@ -3368,7 +3409,7 @@ 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_dev_io_ioctl, DEVICE(vdev), false);
vdev->nv_gpudirect_clique = 0xFF; diff --git a/hw/vfio/platform.c b/hw/vfio/platform.c
index f491f4dc95..51534fd941 100644
--- a/hw/vfio/platform.c
+++ b/hw/vfio/platform.c
@@ -648,7 +648,7 @@ 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_dev_io_ioctl, DEVICE(vdev), false);
  }
#ifdef CONFIG_IOMMUFD
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index 304030e71d..3512556590 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -116,6 +116,7 @@ typedef struct VFIOIOMMUFDContainer {
  OBJECT_DECLARE_SIMPLE_TYPE(VFIOIOMMUFDContainer, VFIO_IOMMU_IOMMUFD);
typedef struct VFIODeviceOps VFIODeviceOps;
+typedef struct VFIODeviceIO VFIODeviceIO;

I suggest VFIODeviceIOOps
  typedef struct VFIODevice {
      QLIST_ENTRY(VFIODevice) next;
@@ -136,6 +137,7 @@ typedef struct VFIODevice {
      OnOffAuto enable_migration;
      bool migration_events;
      VFIODeviceOps *ops;
+    VFIODeviceIO *io;

io_ops

      unsigned int num_irqs;
      unsigned int num_regions;
      unsigned int flags;
@@ -186,6 +188,29 @@ struct VFIODeviceOps {
      int (*vfio_load_config)(VFIODevice *vdev, QEMUFile *f);
  };
+#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 VFIODeviceIO {
+    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);
+};
+
+extern VFIODeviceIO vfio_dev_io_ioctl;

vfio_dev_io_ops_ioctl

+> +#endif /* CONFIG_LINUX */
+
  typedef struct VFIOGroup {
      int fd;
      int groupid;
@@ -317,6 +342,6 @@ int vfio_get_dirty_bitmap(const VFIOContainerBase 
*bcontainer, uint64_t iova,
  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);
+                      VFIODeviceIO *io, DeviceState *dev, bool ram_discard);

VFIODeviceIOOps *io_ops

  int vfio_device_get_aw_bits(VFIODevice *vdev);
  #endif /* HW_VFIO_VFIO_COMMON_H */

Just minor changes. Looks good.

Thanks,

C.




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