On 14.05.2010, at 18:17, Jan Kiszka wrote: > Alexander Graf wrote: >> On 12.05.2010, at 20:51, Jan Kiszka wrote: >> >>> Alexander Graf wrote: >>>> Jan Kiszka wrote: >>>>> Alexander Graf wrote: >>>>> >>>>>> Jan Kiszka wrote: >>>>>> >>>>>>> Move the buffer flush from mux_chr_read to mux_chr_can_read. While the >>>>>>> latter is called periodically, the former will only be invoked when new >>>>>>> characters arrive at the back-end. This caused problems to front-end >>>>>>> drivers whenever they were unable to read data immediately, e.g. >>>>>>> virtio-console attached to stdio. >>>>>>> >>>>>>> >>>>>> I don't see this patch applied, but also don't see any issues with >>>>>> virtio-console anymore on today's git. Odd. >>>>>> >>>>>> >>>>> Hmm, I had a clear before-after experience using virtio console with an >>>>> x86 Linux guest. I still think my patch is correct and required. Maybe >>>>> you can bisect this positive "regression"? Something might paper over >>>>> the core issue now. >>>>> >>>> I just did a git reset --hard on >>>> baf0b55a9e57b909b1f8b0f732c0b10242867418 and it worked! What the ... >>> Whatever "worked" now means (I'm slightly confused), I just rechecked >>> the situation over current git head ("qemu linux-guest.img -chardev >>> stdio,id=cons,mux=on -device virtio-serial -device >>> virtconsole,chardev=cons -mon chardev=cons", "cat /dev/hvc0" in the >>> guest, typing some chars on the host console): The problem still >>> persists, my patch still solves it. Can you confirm this, ideally also >>> for s390? >> >> Now that I can finally reproduce the bug with --enable-io-thread, I can >> verify that it does *not* fix the issue. > > I do not trust your tests. :p > > I just tried to reproduce with --enable-io-thread and the setup I > described above - all still fine here. Can you reproduce with an x86 guest?
Nope, it works fine with an x86 guest. I put the following in /etc/inittab of my guest: 11:2345:respawn:/sbin/mingetty --noclear /dev/hvc0 linux One major thing to keep in mind when talking about s390 guests is that we almost never trap into userspace. Alex