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[Qemu-devel] [PATCH 04/10] vga: make display updates thread safe.
From: |
Gerd Hoffmann |
Subject: |
[Qemu-devel] [PATCH 04/10] vga: make display updates thread safe. |
Date: |
Tue, 4 Apr 2017 12:23:09 +0200 |
The vga code clears the dirty bits *after* reading the framebuffer
memory. So if the guest framebuffer updates hits the race window
between vga reading the framebuffer and vga clearing the dirty bits
vga will miss that update
Fix it by using the new memory_region_copy_and_clear_dirty()
memory_region_copy_get_dirty() functions. That way we clear the
dirty bitmap before reading the framebuffer. Any guest display
updates happening in parallel will be properly tracked in the
dirty bitmap then and the next display refresh will pick them up.
Problem triggers with mttcg only. Before mttcg was merged tcg
never ran in parallel to vga emulation. Using kvm will hide the
problem too, due to qemu operating on a userspace copy of the
kernel's dirty bitmap.
Signed-off-by: Gerd Hoffmann <address@hidden>
---
hw/display/vga.c | 36 +++++++++++++++++-------------------
1 file changed, 17 insertions(+), 19 deletions(-)
diff --git a/hw/display/vga.c b/hw/display/vga.c
index f320946..9bb71f1 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1465,7 +1465,8 @@ static void vga_draw_graphic(VGACommonState *s, int
full_update)
DisplaySurface *surface = qemu_console_surface(s->con);
int y1, y, update, linesize, y_start, double_scan, mask, depth;
int width, height, shift_control, line_offset, bwidth, bits;
- ram_addr_t page0, page1, page_min, page_max;
+ ram_addr_t page0, page1;
+ DirtyBitmapSnapshot *snap = NULL;
int disp_width, multi_scan, multi_run;
uint8_t *d;
uint32_t v, addr1, addr;
@@ -1480,9 +1481,6 @@ static void vga_draw_graphic(VGACommonState *s, int
full_update)
full_update |= update_basic_params(s);
- if (!full_update)
- vga_sync_dirty_bitmap(s);
-
s->get_resolution(s, &width, &height);
disp_width = width;
@@ -1625,11 +1623,17 @@ static void vga_draw_graphic(VGACommonState *s, int
full_update)
addr1 = (s->start_addr * 4);
bwidth = (width * bits + 7) / 8;
y_start = -1;
- page_min = -1;
- page_max = 0;
d = surface_data(surface);
linesize = surface_stride(surface);
y1 = 0;
+
+ if (!full_update) {
+ vga_sync_dirty_bitmap(s);
+ snap = memory_region_snapshot_and_clear_dirty(&s->vram, addr1,
+ bwidth * height,
+ DIRTY_MEMORY_VGA);
+ }
+
for(y = 0; y < height; y++) {
addr = addr1;
if (!(s->cr[VGA_CRTC_MODE] & 1)) {
@@ -1644,17 +1648,17 @@ static void vga_draw_graphic(VGACommonState *s, int
full_update)
update = full_update;
page0 = addr;
page1 = addr + bwidth - 1;
- update |= memory_region_get_dirty(&s->vram, page0, page1 - page0,
- DIRTY_MEMORY_VGA);
+ if (full_update) {
+ update = 1;
+ } else {
+ update = memory_region_snapshot_get_dirty(&s->vram, snap,
+ page0, page1 - page0);
+ }
/* explicit invalidation for the hardware cursor (cirrus only) */
update |= vga_scanline_invalidated(s, y);
if (update) {
if (y_start < 0)
y_start = y;
- if (page0 < page_min)
- page_min = page0;
- if (page1 > page_max)
- page_max = page1;
if (!(is_buffer_shared(surface))) {
vga_draw_line(s, d, s->vram_ptr + addr, width);
if (s->cursor_draw_line)
@@ -1687,13 +1691,7 @@ static void vga_draw_graphic(VGACommonState *s, int
full_update)
dpy_gfx_update(s->con, 0, y_start,
disp_width, y - y_start);
}
- /* reset modified pages */
- if (page_max >= page_min) {
- memory_region_reset_dirty(&s->vram,
- page_min,
- page_max - page_min,
- DIRTY_MEMORY_VGA);
- }
+ g_free(snap);
memset(s->invalidated_y_table, 0, sizeof(s->invalidated_y_table));
}
--
2.9.3
- [Qemu-devel] [PATCH 06/10] cg3: fix up size parameter for memory_region_get_dirty(), (continued)
- [Qemu-devel] [PATCH 06/10] cg3: fix up size parameter for memory_region_get_dirty(), Gerd Hoffmann, 2017/04/04
- [Qemu-devel] [PATCH 10/10] [testing] console: remove do_safe_dpy_refresh, Gerd Hoffmann, 2017/04/04
- [Qemu-devel] [PATCH 03/10] vga: add vga_scanline_invalidated helper, Gerd Hoffmann, 2017/04/04
- [Qemu-devel] [PATCH 08/10] tcx: introduce tcx_check_dirty() function, Gerd Hoffmann, 2017/04/04
- [Qemu-devel] [PATCH 05/10] cg3: remove TARGET_PAGE_SIZE rounding on dirty page detection, Gerd Hoffmann, 2017/04/04
- [Qemu-devel] [PATCH 01/10] bitmap: add bitmap_copy_and_clear_atomic, Gerd Hoffmann, 2017/04/04
- [Qemu-devel] [PATCH 07/10] cg3: make display updates thread safe, Gerd Hoffmann, 2017/04/04
- [Qemu-devel] [PATCH 04/10] vga: make display updates thread safe.,
Gerd Hoffmann <=
- Re: [Qemu-devel] [PATCH 00/10] make display updates thread safe., Mark Cave-Ayland, 2017/04/04