vfio-user: implement VFIO_USER_REGION_READ/WRITE

Originally-by: John Johnson <john.g.johnson@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250625193012.2316242-8-john.levon@nutanix.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

3 files changed, 92 insertions, 0 deletions

diff --git a/hw/vfio-user/device.c b/hw/vfio-user/device.c
index d90232a..4ef6a2d 100644
--- a/hw/vfio-user/device.c
+++ b/hw/vfio-user/device.c
@@ -121,9 +121,88 @@ static int vfio_user_device_io_get_region_info(VFIODevice *vbasedev,
     return 0;
 }
 
+static int vfio_user_device_io_region_read(VFIODevice *vbasedev, uint8_t index,
+                                           off_t off, uint32_t count,
+                                           void *data)
+{
+    g_autofree VFIOUserRegionRW *msgp = NULL;
+    VFIOUserProxy *proxy = vbasedev->proxy;
+    int size = sizeof(*msgp) + count;
+    Error *local_err = NULL;
+
+    if (count > proxy->max_xfer_size) {
+        return -EINVAL;
+    }
+
+    msgp = g_malloc0(size);
+    vfio_user_request_msg(&msgp->hdr, VFIO_USER_REGION_READ, sizeof(*msgp), 0);
+    msgp->offset = off;
+    msgp->region = index;
+    msgp->count = count;
+    trace_vfio_user_region_rw(msgp->region, msgp->offset, msgp->count);
+
+    if (!vfio_user_send_wait(proxy, &msgp->hdr, NULL, size, &local_err)) {
+        error_prepend(&local_err, "%s: ", __func__);
+        error_report_err(local_err);
+        return -EFAULT;
+    }
+
+    if (msgp->hdr.flags & VFIO_USER_ERROR) {
+        return -msgp->hdr.error_reply;
+    } else if (msgp->count > count) {
+        return -E2BIG;
+    } else {
+        memcpy(data, &msgp->data, msgp->count);
+    }
+
+    return msgp->count;
+}
+
+static int vfio_user_device_io_region_write(VFIODevice *vbasedev, uint8_t index,
+                                            off_t off, unsigned count,
+                                            void *data, bool post)
+{
+    g_autofree VFIOUserRegionRW *msgp = NULL;
+    VFIOUserProxy *proxy = vbasedev->proxy;
+    int size = sizeof(*msgp) + count;
+    Error *local_err = NULL;
+    int ret;
+
+    if (count > proxy->max_xfer_size) {
+        return -EINVAL;
+    }
+
+    msgp = g_malloc0(size);
+    vfio_user_request_msg(&msgp->hdr, VFIO_USER_REGION_WRITE, size, 0);
+    msgp->offset = off;
+    msgp->region = index;
+    msgp->count = count;
+    memcpy(&msgp->data, data, count);
+    trace_vfio_user_region_rw(msgp->region, msgp->offset, msgp->count);
+
+    /* Ignore post: all writes are synchronous/non-posted. */
+
+    if (!vfio_user_send_wait(proxy, &msgp->hdr, NULL, 0, &local_err)) {
+        error_prepend(&local_err, "%s: ", __func__);
+        error_report_err(local_err);
+        return -EFAULT;
+    }
+
+    if (msgp->hdr.flags & VFIO_USER_ERROR) {
+        ret = -msgp->hdr.error_reply;
+    } else {
+        ret = count;
+    }
+
+    return ret;
+}
+
 /*
  * Socket-based io_ops
  */
 VFIODeviceIOOps vfio_user_device_io_ops_sock = {
     .get_region_info = vfio_user_device_io_get_region_info,
+    .region_read = vfio_user_device_io_region_read,
+    .region_write = vfio_user_device_io_region_write,
+
 };
diff --git a/hw/vfio-user/protocol.h b/hw/vfio-user/protocol.h
index db88f5f..0cd32ad 100644
--- a/hw/vfio-user/protocol.h
+++ b/hw/vfio-user/protocol.h
@@ -138,4 +138,16 @@ typedef struct {
     uint64_t offset;
 } VFIOUserRegionInfo;
 
+/*
+ * VFIO_USER_REGION_READ
+ * VFIO_USER_REGION_WRITE
+ */
+typedef struct {
+    VFIOUserHdr hdr;
+    uint64_t offset;
+    uint32_t region;
+    uint32_t count;
+    char data[];
+} VFIOUserRegionRW;
+
 #endif /* VFIO_USER_PROTOCOL_H */
diff --git a/hw/vfio-user/trace-events b/hw/vfio-user/trace-events
index ef3f14c..733313c 100644
--- a/hw/vfio-user/trace-events
+++ b/hw/vfio-user/trace-events
@@ -10,3 +10,4 @@ vfio_user_send_write(uint16_t id, int wrote) " id 0x%x wrote 0x%x"
 vfio_user_version(uint16_t major, uint16_t minor, const char *caps) " major %d minor %d caps: %s"
 vfio_user_get_info(uint32_t nregions, uint32_t nirqs) " #regions %d #irqs %d"
 vfio_user_get_region_info(uint32_t index, uint32_t flags, uint64_t size) " index %d flags 0x%x size 0x%"PRIx64
+vfio_user_region_rw(uint32_t region, uint64_t off, uint32_t count) " region %d offset 0x%"PRIx64" count %d"