100% host CPU when enabling Serial Port with Host Pipe mode

[Richard Thomas]

VirtualBox uses 100% of one core of my CPU on my dual-core laptop when I launch a guest OS with an enabled Serial Port. Specifically Port Number: COM1 Port Mode: Host Pipe Create Pipe: (Unchecked) Port/File Path: COM1

Changing Port Mode from Host Pipe to Host Device reduces idle CPU usage to less than 5%. The HELP does not explain the difference between what a Host Pipe is and what a Host Device is. Should the Host Pipe mode really use 100% of a core when guest is idle?

OS details: Windows XP Pro Host 32-bit (fully updated), 3Gb RAM, Dual-Core Intel Core2Duo 2.4GHz. Windows XP Pro Guest 32-bit (fully updated)

[Frank Mehnert]

Of course this is a bug but unfortunately we are not able to reproduce it. Regarding the documentation: I think it is quite verbose. Section 3.9 describes the difference between connecting the guest port to a physical device on the host and connecting to a (virtual) host pipe.

[Richard Thomas]

Sorry that you cannot reproduce it. A quick comment on your statement "I think it is quite verbose". The VBox Manager Serial Ports settings has a Port Mode list with four items (Disconnected, Host Pipe, Host Device, Raw File), and the help section 3.9 refers to THREE options, which it doesn't identify, but in their written order seem to refer to Disconnceted, Host Device and Host Pipe - which is a different order to the Port Mode list. In my naivety as a relatively inadvanced user, I did not know what a Host Pipe was, but the second item in the help read as being what I wanted, so I selected the second item in the Port Mode list, which it unfortunately Host Pipe. This is where my problems began. Might I suggest someone improves the help to:

1. discuss the items in the same order they appear in the list
2. identify the items in the list by name
3. include the missing item Raw File

Thanks

[dlaffoon]

I'm seeing a similar issue with v4.1.0. Win7 host, QNX6.5 guest OS. When I have serial ports with host pipe option selected, the virtual machine consumes 50% CPU of my host PC (dual Xeon X5260 @ 3.33GHz). I was trying to run multiple instances, but running two virtual machines with these settings consumed 100% CPU and made all PCs (guest and host) unresponsive. If I use host device mode, I do not have this issue. Thanks

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.