On Sat, Jul 23, 2011 at 06:13:04PM +1000, Callum Gibson wrote: > On 22Jul11 08:16, John Baldwin wrote: > }The problem is that we calibrate the TSC using this algorithm: > } > } - grab the TSC > } - spin on the ISA timer waiting for it to run for a second > } - grab the TSC > } > }The issue is that the SMI# fires at the same time we want to be execuiting > }step 3, and step 3 is deferred while the SMI# handler runs. As a result, > the > }TSC delta ends up being "1 second + time of an SMI# to poll USB". We have a > }hack fix for this at work that originally came from Attilio Rao. This is a > }patch for it relative to 8. It disables interrupt generation for the ISA > }timer while we calibrate the TSC (which disables the SMI# temporarily): > > Thanks, John. The hack works as intended, but I guess it's not a "real" > solution which is why you haven't committed it?
This sort of thing is going to have to get dealt with officially sooner or later, hack-fix or elegant solution either way[1]. More and more systems are using native USB keyboards, and most system BIOSes I've seen (from multiple vendors, specifically Supermicro, Lenovo, Asus, Dell, HP, and Gigabyte[2]) are defaulting to having these options enabled (and rightfully so). If the hack-fix has repercussions, it would be helpful to know what those are or how those might manifest themselves. Otherwise, has anyone taken a look at how Linux addresses this problem? To my knowledge GRUB and similar bootstraps do not have a native USB stack, so I'm left wondering how they deal with this. [1]: I'm in no way saying "Hey! Fix this! {contributes nothing}", I'm simply pointing out that we're at a point where we really don't have much of a choice. The more I read technical explanations from John the more hate x86 architecture. ;-) [2]: On a couple Gigabyte boards I have the default values for said option is enabled (for both keyboard and mouse). -- | Jeremy Chadwick jdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, US | | Making life hard for others since 1977. PGP 4BD6C0CB | _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"