On Friday 21 October 2005 20:24, Gerd Stolpmann wrote: > Hi list, > > I recently tested the hwrng driver. In principal, it works, but it > sometimes eats up all host CPU time. In particular, I can see that the > UML system does a (blocking) read on /dev/hwrng,
Could you please elaborate on that? Who is doing the read, the rng tools? Also, are they doing only a single read (in which case, it's we the ones who are looping and we're broken) or they are astonished by our -EAGAIN and keep trying (in which case, they are broken)? Actually, from looking at the code (arch/um/drivers/random.c:rng_dev_read()) it appears that we _do_ loop ourselves, if the read is blocking. Not sure how to handle that. We could return maybe -EIO, possibly when a rate limit is exceeded (not trivial to do, though - I must learn using timers first). > and that the host > system loops while reading from /dev/random which almost always returns > -EAGAIN. (Found that out with strace, in the hope the output is > correct.) Well, if the host hasn't enough entropy, it's reasonable for it to return -EAGAIN. And we should do the same (the loop is actually executed by the UML code, right?). However, probably the tools inside UML don't expect a lot to get -EAGAIN from an hardware generator. So possibly they are not ready to handle that well. > Nevertheless rngd seems to work, because when killing with SIGUSR1 it > shows some reasonable statistics. > My test setup is as follows: > - Host system: 2.6.12.6 with SKAS3 v8.2 patch > - UML system: 2.6.14-rc5, in SKAS3 mode. > Using rngd from Debian Sarge. > TLS is disabled. > Let me know if you need more information. > Gerd -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade ___________________________________ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it ------------------------------------------------------- This SF.Net email is sponsored by: Power Architecture Resource Center: Free content, downloads, discussions, and more. http://solutions.newsforge.com/ibmarch.tmpl _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
