[PATCH 0/2] use trace events and fix garbled output

[PATCH 0/2] use trace events and fix garbled output

[Carwyn Ellis]

This patchset supersedes the earlier submission and incorporates
feedback from Laurent Vivier and Gerd Hoffmann.

There are two patches addressing the following in the vmware vga display
code

 - use of fprintf to log debug output to STDERR

   This has been replaced with trace events.

 - garbled display due to lost display updates

   This prevents an issue that can cause garbled display output when
   a high number of screen updates are being requested.

   The queue is now flushed when it reaches capacity.

   The code traversing the queue when updates are being applied to the
   display has also been simplified, since we always start the traversal
   at the beginning of the queue to ensure that all updates are applied.

Carwyn Ellis (2):
  hw/display/vmware_vga: replace fprintf calls with trace events
  hw/display/vmware_vga: do not discard screen updates

 hw/display/trace-events |  4 +++
 hw/display/vmware_vga.c | 63 +++++++++++++++++++++--------------------
 2 files changed, 37 insertions(+), 30 deletions(-)

-- 
2.34.1

[PATCH 1/2] hw/display/vmware_vga: replace fprintf calls with trace events

[Carwyn Ellis]

Debug output was always being sent to STDERR.

This has been replaced with trace events.

Signed-off-by: Carwyn Ellis <carwynellis@gmail.com>
---
 hw/display/trace-events |  3 +++
 hw/display/vmware_vga.c | 22 ++++++++++------------
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/hw/display/trace-events b/hw/display/trace-events
index 3a7a2c957f..e1a0d2a88a 100644
--- a/hw/display/trace-events
+++ b/hw/display/trace-events
@@ -21,6 +21,9 @@ vmware_palette_write(uint32_t index, uint32_t value) "index %d, value 0x%x"
 vmware_scratch_read(uint32_t index, uint32_t value) "index %d, value 0x%x"
 vmware_scratch_write(uint32_t index, uint32_t value) "index %d, value 0x%x"
 vmware_setmode(uint32_t w, uint32_t h, uint32_t bpp) "%dx%d @ %d bpp"
+vmware_verify_rect_less_than_zero(const char *name, const char *param, int x) "%s: %s was < 0 (%d)"
+vmware_verify_rect_greater_than_bound(const char *name, const char *param, int bound, int x) "%s: %s was > %d (%d)"
+vmware_verify_rect_surface_bound_exceeded(const char *name, const char *component, int bound, const char *param1, int value1, const char *param2, int value2) "%s: %s > %d (%s: %d, %s, %d)"
 
 # virtio-gpu-base.c
 virtio_gpu_features(bool virgl) "virgl %d"
diff --git a/hw/display/vmware_vga.c b/hw/display/vmware_vga.c
index e2969a6c81..0d32a605a0 100644
--- a/hw/display/vmware_vga.c
+++ b/hw/display/vmware_vga.c
@@ -297,46 +297,44 @@ static inline bool vmsvga_verify_rect(DisplaySurface *surface,
                                       int x, int y, int w, int h)
 {
     if (x < 0) {
-        fprintf(stderr, "%s: x was < 0 (%d)\n", name, x);
+        trace_vmware_verify_rect_less_than_zero(name, "x", x);
         return false;
     }
     if (x > SVGA_MAX_WIDTH) {
-        fprintf(stderr, "%s: x was > %d (%d)\n", name, SVGA_MAX_WIDTH, x);
+        trace_vmware_verify_rect_greater_than_bound(name, "x", SVGA_MAX_WIDTH, x);
         return false;
     }
     if (w < 0) {
-        fprintf(stderr, "%s: w was < 0 (%d)\n", name, w);
+        trace_vmware_verify_rect_less_than_zero(name, "w", w);
         return false;
     }
     if (w > SVGA_MAX_WIDTH) {
-        fprintf(stderr, "%s: w was > %d (%d)\n", name, SVGA_MAX_WIDTH, w);
+        trace_vmware_verify_rect_greater_than_bound(name, "w", SVGA_MAX_WIDTH, w);
         return false;
     }
     if (x + w > surface_width(surface)) {
-        fprintf(stderr, "%s: width was > %d (x: %d, w: %d)\n",
-                name, surface_width(surface), x, w);
+        trace_vmware_verify_rect_surface_bound_exceeded(name, "width", surface_width(surface), "x", x, "w", w);
         return false;
     }
 
     if (y < 0) {
-        fprintf(stderr, "%s: y was < 0 (%d)\n", name, y);
+        trace_vmware_verify_rect_less_than_zero(name, "y", y);
         return false;
     }
     if (y > SVGA_MAX_HEIGHT) {
-        fprintf(stderr, "%s: y was > %d (%d)\n", name, SVGA_MAX_HEIGHT, y);
+        trace_vmware_verify_rect_greater_than_bound(name, "y", SVGA_MAX_HEIGHT, y);
         return false;
     }
     if (h < 0) {
-        fprintf(stderr, "%s: h was < 0 (%d)\n", name, h);
+        trace_vmware_verify_rect_less_than_zero(name, "h", h);
         return false;
     }
     if (h > SVGA_MAX_HEIGHT) {
-        fprintf(stderr, "%s: h was > %d (%d)\n", name, SVGA_MAX_HEIGHT, h);
+        trace_vmware_verify_rect_greater_than_bound(name, "y", SVGA_MAX_HEIGHT, y);
         return false;
     }
     if (y + h > surface_height(surface)) {
-        fprintf(stderr, "%s: update height > %d (y: %d, h: %d)\n",
-                name, surface_height(surface), y, h);
+        trace_vmware_verify_rect_surface_bound_exceeded(name, "height", surface_height(surface), "y", y, "h", h);
         return false;
     }
 
-- 
2.34.1

Re: [PATCH 1/2] hw/display/vmware_vga: replace fprintf calls with trace events

[Philippe Mathieu-Daudé]

On 1/4/22 19:06, Carwyn Ellis wrote:
> Debug output was always being sent to STDERR.
> 
> This has been replaced with trace events.
> 
> Signed-off-by: Carwyn Ellis <carwynellis@gmail.com>
> ---
>  hw/display/trace-events |  3 +++
>  hw/display/vmware_vga.c | 22 ++++++++++------------
>  2 files changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/hw/display/trace-events b/hw/display/trace-events
> index 3a7a2c957f..e1a0d2a88a 100644
> --- a/hw/display/trace-events
> +++ b/hw/display/trace-events
> @@ -21,6 +21,9 @@ vmware_palette_write(uint32_t index, uint32_t value) "index %d, value 0x%x"
>  vmware_scratch_read(uint32_t index, uint32_t value) "index %d, value 0x%x"
>  vmware_scratch_write(uint32_t index, uint32_t value) "index %d, value 0x%x"
>  vmware_setmode(uint32_t w, uint32_t h, uint32_t bpp) "%dx%d @ %d bpp"
> +vmware_verify_rect_less_than_zero(const char *name, const char *param, int x) "%s: %s was < 0 (%d)"
> +vmware_verify_rect_greater_than_bound(const char *name, const char *param, int bound, int x) "%s: %s was > %d (%d)"
> +vmware_verify_rect_surface_bound_exceeded(const char *name, const char *component, int bound, const char *param1, int value1, const char *param2, int value2) "%s: %s > %d (%s: %d, %s, %d)"

"%s: %s > %d (%s: %d, %s: %d)", otherwise:

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

[PATCH 2/2] hw/display/vmware_vga: do not discard screen updates

[Carwyn Ellis]

In certain circumstances, typically when there is lots changing on the
screen, updates will be discarded resulting in garbled output.

This change simplifies the traversal of the display update FIFO queue
when applying updates. We just track the queue length and iterate up to
the end of the queue.

Additionanlly when adding updates to the queue, if the buffer reaches
capacity we force a flush before accepting further events.

Signed-off-by: Carwyn Ellis <carwynellis@gmail.com>
---
 hw/display/trace-events |  1 +
 hw/display/vmware_vga.c | 41 +++++++++++++++++++++++------------------
 2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/hw/display/trace-events b/hw/display/trace-events
index e1a0d2a88a..5e3cdb3fa3 100644
--- a/hw/display/trace-events
+++ b/hw/display/trace-events
@@ -24,6 +24,7 @@ vmware_setmode(uint32_t w, uint32_t h, uint32_t bpp) "%dx%d @ %d bpp"
 vmware_verify_rect_less_than_zero(const char *name, const char *param, int x) "%s: %s was < 0 (%d)"
 vmware_verify_rect_greater_than_bound(const char *name, const char *param, int bound, int x) "%s: %s was > %d (%d)"
 vmware_verify_rect_surface_bound_exceeded(const char *name, const char *component, int bound, const char *param1, int value1, const char *param2, int value2) "%s: %s > %d (%s: %d, %s, %d)"
+vmware_update_rect_delayed_flush(void) "display update FIFO full - forcing flush"
 
 # virtio-gpu-base.c
 virtio_gpu_features(bool virgl) "virgl %d"
diff --git a/hw/display/vmware_vga.c b/hw/display/vmware_vga.c
index 0d32a605a0..e6943005e3 100644
--- a/hw/display/vmware_vga.c
+++ b/hw/display/vmware_vga.c
@@ -80,7 +80,7 @@ struct vmsvga_state_s {
     struct vmsvga_rect_s {
         int x, y, w, h;
     } redraw_fifo[REDRAW_FIFO_LEN];
-    int redraw_fifo_first, redraw_fifo_last;
+    int redraw_fifo_last;
 };
 
 #define TYPE_VMWARE_SVGA "vmware-svga"
@@ -372,33 +372,39 @@ static inline void vmsvga_update_rect(struct vmsvga_state_s *s,
     dpy_gfx_update(s->vga.con, x, y, w, h);
 }
 
-static inline void vmsvga_update_rect_delayed(struct vmsvga_state_s *s,
-                int x, int y, int w, int h)
-{
-    struct vmsvga_rect_s *rect = &s->redraw_fifo[s->redraw_fifo_last++];
-
-    s->redraw_fifo_last &= REDRAW_FIFO_LEN - 1;
-    rect->x = x;
-    rect->y = y;
-    rect->w = w;
-    rect->h = h;
-}
-
 static inline void vmsvga_update_rect_flush(struct vmsvga_state_s *s)
 {
     struct vmsvga_rect_s *rect;
 
     if (s->invalidated) {
-        s->redraw_fifo_first = s->redraw_fifo_last;
+        s->redraw_fifo_last = 0;
         return;
     }
     /* Overlapping region updates can be optimised out here - if someone
      * knows a smart algorithm to do that, please share.  */
-    while (s->redraw_fifo_first != s->redraw_fifo_last) {
-        rect = &s->redraw_fifo[s->redraw_fifo_first++];
-        s->redraw_fifo_first &= REDRAW_FIFO_LEN - 1;
+    for (int i = 0; i < s->redraw_fifo_last; i++) {
+        rect = &s->redraw_fifo[i];
         vmsvga_update_rect(s, rect->x, rect->y, rect->w, rect->h);
     }
+
+    s->redraw_fifo_last = 0;
+}
+
+static inline void vmsvga_update_rect_delayed(struct vmsvga_state_s *s,
+                int x, int y, int w, int h)
+{
+
+    if (s->redraw_fifo_last >= REDRAW_FIFO_LEN) {
+        trace_vmware_update_rect_delayed_flush();
+        vmsvga_update_rect_flush(s);
+    }
+
+    struct vmsvga_rect_s *rect = &s->redraw_fifo[s->redraw_fifo_last++];
+
+    rect->x = x;
+    rect->y = y;
+    rect->w = w;
+    rect->h = h;
 }
 
 #ifdef HW_RECT_ACCEL
@@ -1151,7 +1157,6 @@ static void vmsvga_reset(DeviceState *dev)
     s->config = 0;
     s->svgaid = SVGA_ID;
     s->cursor.on = 0;
-    s->redraw_fifo_first = 0;
     s->redraw_fifo_last = 0;
     s->syncing = 0;
 
-- 
2.34.1