[Spice-devel] [PATCH] miniport/qxl: FillVideoMode: only allow word aligned strides

[Alon Levy]

This is a pixman requirement. If it isn't enforced spice crashes, qemu
with it. That should be fixed, but there is no simple way to allow for
non word aligned strides, and the only down side is that for 16 bit
modes we will require even widths. And we already have the same
implementation detail in the X driver, only there it is a multiple of 8,
not 4.
---
 miniport/qxl.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/miniport/qxl.c b/miniport/qxl.c
index 55e55d3..f177d91 100644
--- a/miniport/qxl.c
+++ b/miniport/qxl.c
@@ -469,17 +469,24 @@ VP_STATUS FillVidModeInfo(VIDEO_MODE_INFORMATION *pMode, ULONG xres, ULONG yres,
 /* Fills given video mode structure */
 VP_STATUS FillVidModeInfo(VIDEO_MODE_INFORMATION *pMode, ULONG xres, ULONG yres, ULONG bpp, ULONG index)
 {
+    unsigned bytes_pp = (bpp + 7) / 8;
+
     if (xres <= 0 || yres <= 0)
         return ERROR_INVALID_DATA;
 
     VideoPortZeroMemory(pMode, sizeof(VIDEO_MODE_INFORMATION));
 
+    /* Honor pixmap's stride % 4 == 0 limitation. Pixmap is used by spice-server. */
+    if (xres * bytes_pp % 4 != 0) {
+        xres = ((xres * bytes_pp) & ~0x3) / bytes_pp;
+    }
+
     /*Common entries*/
     pMode->Length                       = sizeof(VIDEO_MODE_INFORMATION);
     pMode->ModeIndex                    = index;
     pMode->VisScreenWidth               = xres;
     pMode->VisScreenHeight              = yres;
-    pMode->ScreenStride                 = xres * ((bpp + 7) / 8);
+    pMode->ScreenStride                 = xres * bytes_pp;
     pMode->NumberOfPlanes               = 1;
     pMode->BitsPerPlane                 = bpp;
     pMode->Frequency                    = 60;
-- 
1.7.12.1