Plumb through vfio_device_get_feature to the vfio-user server. Note that
we translate EINVAL into ENOTTY, as the existing generic vfio code is
expecting the latter to mean "unsupported".

As part of adding a trace point, clean up the trace file.

Signed-off-by: John Levon <john.levon@nutanix.com>
---
 hw/vfio-user/protocol.h   | 12 +++++++++++
 hw/vfio-user/device.c     | 42 +++++++++++++++++++++++++++++++++++++++
 hw/vfio-user/trace-events | 23 +++++++++++----------
 3 files changed, 67 insertions(+), 10 deletions(-)

diff --git a/hw/vfio-user/protocol.h b/hw/vfio-user/protocol.h
index 3249a4a6b6..2a0c31e7c5 100644
--- a/hw/vfio-user/protocol.h
+++ b/hw/vfio-user/protocol.h
@@ -40,6 +40,7 @@ enum vfio_user_command {
     VFIO_USER_DEVICE_RESET              = 13,
     VFIO_USER_DIRTY_PAGES               = 14,
     VFIO_USER_REGION_WRITE_MULTI        = 15,
+    VFIO_USER_DEVICE_FEATURE            = 16,
     VFIO_USER_MAX,
 };
 
@@ -239,4 +240,15 @@ typedef struct {
     VFIOUserWROne wrs[VFIO_USER_MULTI_MAX];
 } VFIOUserWRMulti;
 
+/*
+ * VFIO_USER_DEVICE_FEATURE
+ * imported from struct vfio_device_feature
+ */
+typedef struct {
+    VFIOUserHdr hdr;
+    uint32_t argsz;
+    uint32_t flags;
+    char data[];
+} VFIOUserDeviceFeature;
+
 #endif /* VFIO_USER_PROTOCOL_H */
diff --git a/hw/vfio-user/device.c b/hw/vfio-user/device.c
index 64ef35b320..b8d2b7c1a8 100644
--- a/hw/vfio-user/device.c
+++ b/hw/vfio-user/device.c
@@ -74,6 +74,47 @@ void vfio_user_device_reset(VFIOUserProxy *proxy)
     }
 }
 
+static int
+vfio_user_device_io_device_feature(VFIODevice *vbasedev,
+                                   struct vfio_device_feature *feature)
+{
+    g_autofree VFIOUserDeviceFeature *msgp = NULL;
+    int size = sizeof(VFIOUserHdr) + feature->argsz;
+    VFIOUserProxy *proxy = vbasedev->proxy;
+    Error *local_err = NULL;
+
+    msgp = g_malloc0(size);
+
+    vfio_user_request_msg(&msgp->hdr, VFIO_USER_DEVICE_FEATURE, size, 0);
+
+    memcpy(&msgp->argsz, &feature->argsz, feature->argsz);
+
+    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) {
+        /*
+         * Client expects ENOTTY for "not supported", but the protocol may
+         * return EINVAL (which should only occur in the case the feature isn't
+         * actually supported on the server).
+         */
+        if (msgp->hdr.error_reply == EINVAL) {
+            return -ENOTTY;
+        }
+
+        return -msgp->hdr.error_reply;
+    }
+
+    memcpy(feature, &msgp->argsz, feature->argsz);
+
+    trace_vfio_user_device_io_device_feature(msgp->argsz, msgp->flags);
+
+    return 0;
+}
+
 static int vfio_user_get_region_info(VFIOUserProxy *proxy,
                                      struct vfio_region_info *info,
                                      VFIOUserFDs *fds)
@@ -432,6 +473,7 @@ static int vfio_user_device_io_region_write(VFIODevice *vbasedev, uint8_t index,
  * Socket-based io_ops
  */
 VFIODeviceIOOps vfio_user_device_io_ops_sock = {
+    .device_feature = vfio_user_device_io_device_feature,
     .get_region_info = vfio_user_device_io_get_region_info,
     .get_irq_info = vfio_user_device_io_get_irq_info,
     .set_irqs = vfio_user_device_io_set_irqs,
diff --git a/hw/vfio-user/trace-events b/hw/vfio-user/trace-events
index abb67f4c11..503e1c82d4 100644
--- a/hw/vfio-user/trace-events
+++ b/hw/vfio-user/trace-events
@@ -2,19 +2,22 @@
 #
 # SPDX-License-Identifier: GPL-2.0-or-later
 
-# common.c
+# container.c
+vfio_user_dma_map(uint64_t iova, uint64_t size, uint64_t off, uint32_t flags, bool async_ops) " iova 0x%"PRIx64" size 0x%"PRIx64" off 0x%"PRIx64" flags 0x%x async_ops %d"
+vfio_user_dma_unmap(uint64_t iova, uint64_t size, uint32_t flags,  bool async_ops) " iova 0x%"PRIx64" size 0x%"PRIx64" flags 0x%x async_ops %d"
+
+# device.c
+vfio_user_device_io_device_feature(uint32_t argsz, uint32_t flags) " argsz 0x%x flags 0x%x"
+vfio_user_get_info(uint32_t nregions, uint32_t nirqs) " #regions %d #irqs %d"
+vfio_user_get_irq_info(uint32_t index, uint32_t flags, uint32_t count) " index %d flags 0x%x count %d"
+vfio_user_set_irqs(uint32_t index, uint32_t start, uint32_t count, uint32_t flags) " index %d start %d count %d flags 0x%x"
+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"
+
+# proxy.c
 vfio_user_recv_hdr(const char *name, uint16_t id, uint16_t cmd, uint32_t size, uint32_t flags) " (%s) id 0x%x cmd 0x%x size 0x%x flags 0x%x"
 vfio_user_recv_read(uint16_t id, int read) " id 0x%x read 0x%x"
 vfio_user_recv_request(uint16_t cmd) " command 0x%x"
 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"
-vfio_user_get_irq_info(uint32_t index, uint32_t flags, uint32_t count) " index %d flags 0x%x count %d"
-vfio_user_set_irqs(uint32_t index, uint32_t start, uint32_t count, uint32_t flags) " index %d start %d count %d flags 0x%x"
 vfio_user_wrmulti(const char *s, uint64_t wr_cnt) " %s count 0x%"PRIx64
-
-# container.c
-vfio_user_dma_map(uint64_t iova, uint64_t size, uint64_t off, uint32_t flags, bool async_ops) " iova 0x%"PRIx64" size 0x%"PRIx64" off 0x%"PRIx64" flags 0x%x async_ops %d"
-vfio_user_dma_unmap(uint64_t iova, uint64_t size, uint32_t flags,  bool async_ops) " iova 0x%"PRIx64" size 0x%"PRIx64" flags 0x%x async_ops %d"
-- 
2.43.0