[Qemu-devel] [PATCH v3 4/4] hw/qxl-render: drop cursor locks, replace with pipe

[Alon Levy <alevy@redhat.com>]

Switching locking protection of ds->cursor_set/cursor_move to moving
every call to these functions into the iothread and using the ssd->pipe
to transfer that, adding QXL_SERVER_CURSOR_SET, QXL_SERVER_CURSOR_MOVE.

This is tested with both -vnc :0 -spice and -sdl -spice.
---
 hw/qxl-render.c    |   25 +++++++++-----
 hw/qxl.c           |   90 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 hw/qxl.h           |    4 ++
 ui/spice-display.h |   13 +++++++-
 4 files changed, 122 insertions(+), 10 deletions(-)

diff --git a/hw/qxl-render.c b/hw/qxl-render.c
index 58965e0..6759edb 100644
--- a/hw/qxl-render.c
+++ b/hw/qxl-render.c
@@ -178,7 +178,6 @@ fail:
     return NULL;
 }
 
-
 /* called from spice server thread context only */
 void qxl_render_cursor(PCIQXLDevice *qxl, QXLCommandExt *ext)
 {
@@ -209,18 +208,26 @@ void qxl_render_cursor(PCIQXLDevice *qxl, QXLCommandExt *ext)
         if (c == NULL) {
             c = cursor_builtin_left_ptr();
         }
-        qemu_mutex_lock_iothread();
-        qxl->ssd.ds->cursor_define(c);
-        qxl->ssd.ds->mouse_set(x, y, 1);
-        qemu_mutex_unlock_iothread();
-        cursor_put(c);
+        qxl_server_request_cursor_set(qxl, c, x, y);
         break;
     case QXL_CURSOR_MOVE:
         x = cmd->u.position.x;
         y = cmd->u.position.y;
-        qemu_mutex_lock_iothread();
-        qxl->ssd.ds->mouse_set(x, y, 1);
-        qemu_mutex_unlock_iothread();
+        qxl_server_request_cursor_move(qxl, x, y);
         break;
     }
 }
+
+/* called from iothread only (via qxl.c:pipe_read) */
+void qxl_render_cursor_set(SimpleSpiceDisplay *ssd, QEMUCursor *c, int x, int y)
+{
+    ssd->ds->cursor_define(c);
+    ssd->ds->mouse_set(x, y, 1);
+    cursor_put(c);
+}
+
+/* called from iothread only (via qxl.c:pipe_read) */
+void qxl_render_cursor_move(SimpleSpiceDisplay *ssd, int x, int y)
+{
+    ssd->ds->mouse_set(x, y, 1);
+}
diff --git a/hw/qxl.c b/hw/qxl.c
index cf3c938..4c27deb 100644
--- a/hw/qxl.c
+++ b/hw/qxl.c
@@ -117,6 +117,27 @@ static QXLMode qxl_modes[] = {
 #endif
 };
 
+typedef struct __attribute__ ((__packed__)) {
+    QEMUCursor *c;
+    int x;
+    int y;
+} QXLServerCursorSet;
+
+typedef struct __attribute__ ((__packed__)) {
+    int x;
+    int y;
+} QXLServerCursorMove;
+
+typedef struct __attribute__ ((__packed__)) {
+    unsigned char req;
+    QXLServerCursorMove data;
+} QXLServerCursorMoveRequest;
+
+typedef struct __attribute__ ((__packed__)) {
+    unsigned char req;
+    QXLServerCursorSet data;
+} QXLServerCursorSetRequest;
+
 static PCIQXLDevice *qxl0;
 
 static void qxl_send_events(PCIQXLDevice *d, uint32_t events);
@@ -337,6 +358,33 @@ static void interface_get_init_info(QXLInstance *sin, QXLDevInitInfo *info)
 }
 
 /* called from spice server thread context only */
+void qxl_server_request_cursor_set(PCIQXLDevice *qxl, QEMUCursor *c, int x, int y)
+{
+    QXLServerCursorSetRequest req;
+    int r;
+
+    req.req = QXL_SERVER_CURSOR_SET;
+    req.data.c = c;
+    req.data.x = x;
+    req.data.y = y;
+    r = write(qxl->ssd.pipe[1], &req, sizeof(req));
+    assert(r == sizeof(req));
+}
+
+/* called from spice server thread context only */
+void qxl_server_request_cursor_move(PCIQXLDevice *qxl, int x, int y)
+{
+    QXLServerCursorMoveRequest req;
+    int r;
+
+    req.req = QXL_SERVER_CURSOR_MOVE;
+    req.data.x = x;
+    req.data.y = y;
+    r = write(qxl->ssd.pipe[1], &req, sizeof(req));
+    assert(r == sizeof(req));
+}
+
+/* called from spice server thread context only */
 static int interface_get_command(QXLInstance *sin, struct QXLCommandExt *ext)
 {
     PCIQXLDevice *qxl = container_of(sin, PCIQXLDevice, ssd.qxl);
@@ -1055,12 +1103,37 @@ static void qxl_map(PCIDevice *pci, int region_num,
     }
 }
 
+static void read_bytes(int fd, void *buf, int len_requested)
+{
+    int len;
+    int total_len = 0;
+
+    do {
+        len = read(fd, buf, len_requested - total_len);
+        if (len < 0) {
+            if (errno == EINTR || errno == EAGAIN) {
+                continue;
+            }
+            perror("qxl: pipe_read: read failed");
+            /* will abort once it's out of the while loop */
+            break;
+        }
+        total_len += len;
+        buf = (uint8_t *)buf + len;
+    } while (total_len < len_requested);
+    assert(total_len == len_requested);
+}
+
 static void pipe_read(void *opaque)
 {
     SimpleSpiceDisplay *ssd = opaque;
     unsigned char cmd;
     int len, set_irq = 0;
     int create_update = 0;
+    int cursor_set = 0;
+    int cursor_move = 0;
+    QXLServerCursorSet cursor_set_data;
+    QXLServerCursorMove cursor_move_data;
 
     while (1) {
         cmd = 0;
@@ -1082,6 +1155,17 @@ static void pipe_read(void *opaque)
         case QXL_SERVER_CREATE_UPDATE:
             create_update = 1;
             break;
+        case QXL_SERVER_CURSOR_SET:
+            if (cursor_set == 1) {
+                cursor_put(cursor_set_data.c);
+            }
+            cursor_set = 1;
+            read_bytes(ssd->pipe[0], &cursor_set_data, sizeof(cursor_set_data));
+            break;
+        case QXL_SERVER_CURSOR_MOVE:
+            cursor_move = 1;
+            read_bytes(ssd->pipe[0], &cursor_move_data, sizeof(cursor_move_data));
+            break;
         default:
             fprintf(stderr, "%s: unknown cmd %u\n", __FUNCTION__, cmd);
             abort();
@@ -1099,6 +1183,12 @@ static void pipe_read(void *opaque)
     if (set_irq) {
         qxl_set_irq(container_of(ssd, PCIQXLDevice, ssd));
     }
+    if (cursor_move) {
+        qxl_render_cursor_move(ssd, cursor_move_data.x, cursor_move_data.y);
+    }
+    if (cursor_set) {
+        qxl_render_cursor_set(ssd, cursor_set_data.c, cursor_set_data.x, cursor_set_data.y);
+    }
 }
 
 static void qxl_send_events(PCIQXLDevice *d, uint32_t events)
diff --git a/hw/qxl.h b/hw/qxl.h
index 701245f..f4f99ec 100644
--- a/hw/qxl.h
+++ b/hw/qxl.h
@@ -93,6 +93,8 @@ typedef struct PCIQXLDevice {
 
 /* qxl.c */
 void *qxl_phys2virt(PCIQXLDevice *qxl, QXLPHYSICAL phys, int group_id);
+void qxl_server_request_cursor_set(PCIQXLDevice *qxl, QEMUCursor *c, int x, int y);
+void qxl_server_request_cursor_move(PCIQXLDevice *qxl, int x, int y);
 
 /* qxl-logger.c */
 void qxl_log_cmd_cursor(PCIQXLDevice *qxl, QXLCursorCmd *cmd, int group_id);
@@ -102,3 +104,5 @@ void qxl_log_command(PCIQXLDevice *qxl, const char *ring, QXLCommandExt *ext);
 void qxl_render_resize(PCIQXLDevice *qxl);
 void qxl_render_update(PCIQXLDevice *qxl);
 void qxl_render_cursor(PCIQXLDevice *qxl, QXLCommandExt *ext);
+void qxl_render_cursor_set(SimpleSpiceDisplay *ssd, QEMUCursor *c, int x, int y);
+void qxl_render_cursor_move(SimpleSpiceDisplay *ssd, int x, int y);
diff --git a/ui/spice-display.h b/ui/spice-display.h
index 2be6a34..bbfd689 100644
--- a/ui/spice-display.h
+++ b/ui/spice-display.h
@@ -31,11 +31,22 @@
 
 #define NUM_SURFACES 1024
 
-/* For commands/requests from server thread to iothread */
+/*
+ * Commands/requests from server thread to iothread.
+ * Note that CREATE_UPDATE is used both with qxl and without it (spice-display)
+ * the others are only used with the qxl device.
+ *
+ * SET_IRQ - just the request is sent (1 byte)
+ * CREATE_UPDATE - jus the request is sent (1 byte)
+ * CURSOR_SET - send QXLServerRequestCursorSet
+ * CURSOR_MOVE - send QXLServerRequestCursorMove
+ */
 #define QXL_EMPTY_UPDATE ((void *)-1)
 enum {
     QXL_SERVER_SET_IRQ = 1,
     QXL_SERVER_CREATE_UPDATE,
+    QXL_SERVER_CURSOR_SET,
+    QXL_SERVER_CURSOR_MOVE
 };
 
 struct SimpleSpiceUpdate;
-- 
1.7.4.1