Created attachment 155919 [details] Crop from QEMU screenshot of stripey mouse See attached crop r281777, QEMU screengrab. Also reproduced on a Thinkpad X220 with i950kms and a little older kernel.
Fix in review at https://reviews.freebsd.org/D2360 (VGA will require a similar fix.)
I just discovered that this does not happen on stable/10. The latent bug here was exposed by r278673, which expanded the mouse pointer beyond 8 pixels wide. (https://reviews.freebsd.org/D1801)
A commit references this bug: Author: emaste Date: Wed Apr 29 20:30:11 UTC 2015 New revision: 282247 URL: https://svnweb.freebsd.org/changeset/base/282247 Log: vt: fix vt_fb_bitblt_bitmap mask corruption Previously the mask wrapped when one or more of the mask bytes extended past the right edge of the window. Simplify the logic and use the same byte offset and bit in both the pattern and mask. PR: 199648 Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D2360 Changes: head/sys/dev/vt/hw/fb/vt_fb.c
Other vt drivers likely require a similar change, and then all should be MFC'd to stable/10.
A commit references this bug: Author: emaste Date: Tue May 12 18:08:08 UTC 2015 New revision: 282822 URL: https://svnweb.freebsd.org/changeset/base/282822 Log: MFC r282247: vt: fix vt_fb_bitblt_bitmap mask corruption Previously the mask wrapped when one or more of the mask bytes extended past the right edge of the window. Simplify the logic and use the same byte offset and bit in both the pattern and mask. PR: 199648 Sponsored by: The FreeBSD Foundation Changes: _U stable/10/ stable/10/sys/dev/vt/hw/fb/vt_fb.c