qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Qemu-devel] Re: [PATCH 0/5] Various USB fixes and improvements


From: Anthony Liguori
Subject: [Qemu-devel] Re: [PATCH 0/5] Various USB fixes and improvements
Date: Thu, 14 Aug 2008 12:55:54 -0500
User-agent: Thunderbird 2.0.0.16 (X11/20080723)

Max Krasnyansky wrote:
This patch series started when I tried to share USB ports between four instances of Windows XP running on the same Linux box (under KVM).
I quickly realized that current USB support is not very flexible. We do
not handle devices disconnects, there is not way to assign certain USB
ports to VM instance, etc.

Once I fixed that I discovered that USB devices that I absolutely need
in the VMs (Xilinx and Altera USB dongles) do not really work with
QEMU. VMs were getting stuck, applications unhappy, etc.
So I endded up rewriting UHCI and Linux host USB layers to make them fully async and to support multiple outstanding transactions.

The result is quite nice. We can now assign USB buses to VM instances and devices are automatically connected to the VMs. Just do usb_add host:N.*
in the console or -usbdevice command line option (N is the bus number).
Also when device is disconnected from the host it's automatically removed
from the guest.

Host USB devices operate in fully async mode (except the control transfers).
All the stalls and jerkiness due to long synchronous transactions is gone.
I can easily hook up four different USB devices (mouse, CF card reader, phone, Xilinx dongle) and everything is working perfectly. Mouse movements
are silky smooth :).

I did some profiling with OProfile and we seems to be doing ok while XP is pumping ~10 MBytes over USB (reported by one of the apps I'm using). UHCI stuff is well below VNC for example.

There is more work to be done (async control transfers for example). But I think this is way better than what we have now and is ready for more testing by wider audience. Most of the testing so far was done with KVM flavor of QEMU. I did test generic i386-softmmu target a bit, it's too slow for any serious testing with XP. I did full compile (all targets) too and it went fine.

Altogether this patch series looks very promising. The current USB pass through code is pretty fickle so some clean-up is definitely needed.

I don't understand USB well enough to do a thorough review. I hope others can look through it and provide more detailed feedback. I'll do some testing of it tonight.

Regards,

Anthony Liguori




reply via email to

[Prev in Thread] Current Thread [Next in Thread]