Drunken keyboard in go32v2 programs

QEMU 2.5.0, SeaBIOS 1.9.1; I've been noticing this bug for quite a while, though.

Steps to reproduce:

# Create a VM image, install DOS in it (doesn't matter which) and launch it.
# Launch a "bare DOS" DPMI host (not an operating system) in it; I tested with CWSDPMI and HDPMI32.
# Run a go32v2 program which reads keyboard input (say, the Lua interpreter: <http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.1/repos/devel/lua.zip>; the Free Pascal IDE will also do; on the other hand, DOS/4GW programs seem unaffected).
# Quickly type in something random (e.g. alternate between hitting "p" and "q"), then optionally move the cursor left and right.
# Observe how some keystrokes are missed, and some are caught twice.

The issue does NOT arise:
* on bare metal DOS,
* in VirtualBox,
* in Bochs with stock Plex86 BIOS,
* in Bochs with SeaBIOS,
* in DOSEMU,
* in DOSBox,
* in QEMU when the DPMI host is Windows 3.11/9x
so at this point I'm reasonably sure that it's the fault of either QEMU or SeaBIOS, and probably the former. The issue arises regardless of whether KVM is enabled.