Messages in this thread | | | Date | Mon, 17 Oct 2005 19:26:41 -0400 | From | Jeff Garzik <> | Subject | Re: [RFC] RNG rewrite... |
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H. Peter Anvin wrote: > Followup to: <20051016005341.GB5946@plexity.net> > By author: Deepak Saxena <dsaxena@plexity.net> > In newsgroup: linux.dev.kernel > >>It's a magic regsiter we just read/write and could be done in userspace. >>I also took a look at MPC85xx and it has the same sort of interface but >>also has an error interrupt capability. On second thought a class >>interface is overkill b/c there will only be one RNG per system, so >>I can just do something like watchdogs where we have a bunch of simple >>drivers exposing the same interface. We could do it in user space but >>then we have separate RNG implementations for x86 and !x86 and I'd >>rather not see that. Can we move the x86 code out to userspace and >>just let the daemon eat the numbers directly from HW? We can mmap() >>PCI devices, but I don't know enough about x86 to say whether msr >>instructions can execute out of userspace (or if we want them to...).
> MSR instructions cannot execute out of userspace, but the MSR driver > might be possible to use. It's usually quite slow, however.
MSRs are used for setup, not for actual data.
Intel: magic MMIO address (readb) AMD: magic PIO address (inl) VIA: CPU instruction ('xstore')
Jeff
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