[coreboot] disabling bios usb stack

Scott Duplichan scott at notabs.org
Wed Aug 27 20:43:37 CEST 2014

ron minnich [mailto:rminnich at gmail.com] wrote:

]This is really interesting information, thanks.
]This embedded USB stack problem actually impacts HPC applications.
]This type of periodic interference can cause big troubles when you
]have lots of nodes.
]Look for "the case of the missing supercomputer performance" for a
]classic paper. In that case, a 1/30 hz (i.e. lpd dropping out of
]select every 30 seconds on 2048 nodes) was worth a couple tens of
]millions of dollars of performance.
]I'm amazed that the embedded USB stack problems are WORSE, not better,
]than they were a few years back. The x86 world just keeps getting more
]backwards. I'm sorry to see the ARM V8 world trying to emulate it.

I have seen concern about BIOS SMI overhead from server customers running
certain applications. These customers do not want avoidable interruptions
of even a few uS. Some server BIOS enable a periodic SMI for various server
management uses. This never ending periodic SMI is not wanted by these
customers. But I thought all USB related SMI activity ends after a legacy
BIOS hands control to an operating system that supports USB. For pure
UEFI, I don't believe the USB uses SMI at all. So it would seem like
disabling USB in the operating system would be just as good as doing it
in BIOS. If an OS that predates USB is used, SMI will continue in order
to support legacy 60/64 emulation. In this case, the easiest solution 
might be to set the global SMI mask in the south bridge, assuming this
is the only source of SMI.

On Tue, Aug 26, 2014 at 3:14 PM, Антон Кочков <anton.kochkov at gmail.com> wrote:
> Hello,
> Just checked some binaries - PEI USB driver is loading anyway, no
> checking for any setup option, so I guess it will be very hard even
> with the unpacking UEFI image and removing these drivers. Also in most
> UEFI systems big part of USB driver working in SMM mode, so it will be
> hard to patch this code on the fly.
> Best regards,
> Anton Kochkov.
> On Wed, Aug 27, 2014 at 1:23 AM, Carl-Daniel Hailfinger
> <c-d.hailfinger.devel.2006 at gmx.net> wrote:
>> Hi Ron,
>> Am 26.08.2014 00:22 schrieb ron minnich:
>>> disabling the usb stack is the goal in this case.
>> AFAIK it's called "USB keyboard support", "USB legacy support" or
>> something similar in most BIOSes. This internally maps a USB keyboard to
>> a virtual PS/2 keyboard and sometimes has quite a few issues. If that's
>> what your friend meant, disabling it should be straightforward in the
>> BIOS menu.
>> However, if your friend is a victim of EFI, I fear he is beyond help
>> except for trying coreboot.
>> Regards,
>> Carl-Daniel
>> --
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