Microkernel?

By: dmcq (dmcq.delete@this.fano.co.uk), March 18, 2021 6:30 am
Room: Moderated Discussions
Adrian (a.delete@this.acm.org) on March 18, 2021 4:12 am wrote:
> Michael S (already5chosen.delete@this.yahoo.com) on March 18, 2021 3:32 am wrote:
> > NvaxPlus (anon.delete.delete@this.this.example.com) on March 17, 2021 11:48 am wrote:
> > > Linus Torvalds (torvalds.delete@this.linux-foundation.org) on March 16, 2021 7:25 pm wrote:
> > > > Why is this even a discussion any more? Microkernels failed.
> > > > Give them up. You want a monolithic kernel. End of story.
> > > >
> > >
> > > What possible, useful sense is this true? There are billions
> > > and billions of devices running L4. Stop trafficking
> > > in tropes that were stale 20 years ago. Exactly nothing about microkernels notionally implies share-nothing
> > > message passing between address space isolated processes
> > > as the sole "IPC" (taken broadly) mechanism. In fact,
> > > most don't even work that way. Amazingly, kernel development has actually progressed since Mach.
> > >
> >
> > Is L4 in Qualcomm modems really used as microkernel, with all services running in separate
> > HW-protected memory domains and with each service having at least one thread of its own?
>
>
> I have no idea what Qualcomm does, but I also doubt very much that those small microcontrollers
> have any other kind of memory protection except for the kernel and maybe not even that.
>
> Your doubt is extremely relevant, because in the absence of multiple separate HW-protected memory
> domains there is no difference in the security properties of a microkernel and of a monolithic
> kernel, so the claim that there are billions of devices running microkernels would be false.
>
> However, without HW-memory protection, i.e. without paging and/or segmentation, and likely also without
> caches, the context switches would be very fast so there will also be no differences in performance
> between a kernel structured like a microkernel and a kernel structured as a monolithic kernel.
>
>
> My guess is that the choice of L4 in Qualcomm devices has nothing to do with the fact that
> on CPUs with memory protection it is possible to use L4 as the base of a microkernel, but
> everything to do with the fact that L4 is a small and bug-free kernel (formally proved) and
> for the reduced needs of an embedded microcontroller only relatively little code must be
> added to the kernel, so the additional custom code can hopefully be also bug-free.

32 bit embedded controllers don't normally have virtual memory or caches - but they do typically have quite good memory protection with each task being able to access a number of protection domains or segments at a time. Just because you have a hardware address doesn't mean you can access it.
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TopicPosted ByDate
x86 - why unite when you can fragment?anonymou52021/03/12 06:16 PM
  x86 - why unite when you can fragment?Linus Torvalds2021/03/13 01:18 PM
    x86 - why unite when you can fragment?Jon Masters2021/03/13 07:25 PM
      x86 - why unite when you can fragment?Jon Masters2021/03/13 07:44 PM
        x86 - why unite when you can fragment?Yuhong Bao2021/03/13 08:49 PM
        x86 - why unite when you can fragment?tt2021/03/20 09:30 AM
    x86 - why unite when you can fragment?Andrey2021/03/14 04:15 PM
      x86 - why unite when you can fragment?Linus Torvalds2021/03/14 04:58 PM
        x86 - why unite when you can fragment?anonymou52021/03/14 05:31 PM
          x86 - why unite when you can fragment?anon22021/03/14 08:07 PM
        Microkernel?Anon2021/03/14 11:49 PM
          Microkernel?none2021/03/15 12:37 AM
            Microkernel?Anon2021/03/15 01:56 AM
          Microkernel?anon22021/03/15 01:58 AM
            Microkernel?Simon Farnsworth2021/03/15 03:12 AM
              Microkernel?anon22021/03/15 04:53 AM
                Microkernel?Simon Farnsworth2021/03/15 06:56 AM
                  Microkernel?iz2021/03/15 08:10 AM
                    Microkernel?Anon2021/03/15 09:05 AM
                      Microkernel?iz2021/03/16 01:25 AM
                        Microkernel?Andrey2021/03/16 02:54 AM
                          Microkernel?iz2021/03/16 08:36 AM
                            Microkernel?Andrey2021/03/16 10:06 AM
                              Microkernel?anonymou52021/03/16 11:44 AM
                              Microkernel?iz2021/03/21 02:58 AM
                                Microkernel?Andrey2021/03/21 09:34 AM
                  Microkernel?anon22021/03/15 08:31 AM
                    Microkernel?Simon Farnsworth2021/03/16 04:42 AM
            Microkernel?Gabriele Svelto2021/03/15 03:21 AM
              Microkernel?anon22021/03/15 04:56 AM
                Microkernel?Gabriele Svelto2021/03/15 10:41 AM
                  Microkernel?anon22021/03/15 08:00 PM
                    Microkernel?Gabriele Svelto2021/03/16 07:23 AM
                      Microkernel?anon22021/03/16 05:13 PM
                        Microkernel?anon22021/03/16 05:16 PM
                    Microkernel?Gian-Carlo Pascutto2021/03/16 01:40 PM
                      Microkernel?anon22021/03/16 05:53 PM
                        Microkernel?Linus Torvalds2021/03/16 07:25 PM
                          Microkernel?Doug S2021/03/17 09:30 AM
                            Microkernel?Linus Torvalds2021/03/17 10:30 AM
                              Microkernel?Brendan2021/03/17 10:56 PM
                                Microkernel?Michael S2021/03/18 03:47 AM
                                  Microkernel?Brendan2021/03/18 09:07 AM
                              Microkernel?Jose2021/03/18 09:35 AM
                            Microkernel?zArchJon2021/03/18 05:42 PM
                          TransputerRichardC2021/03/17 09:47 AM
                          Microkernel?dmcq2021/03/17 11:15 AM
                            Microkernel?Linus Torvalds2021/03/17 11:59 AM
                              Microkernel?dmcq2021/03/17 12:38 PM
                              Microkernel?Adrian2021/03/17 01:00 PM
                              Microkernel?Ana R. Riano2021/03/18 04:33 AM
                              Microkernel?2021/04/30 04:52 PM
                          Microkernel?NvaxPlus2021/03/17 11:48 AM
                            Microkernel?Michael S2021/03/18 03:32 AM
                              Microkernel?Adrian2021/03/18 04:12 AM
                                Microkernel?dmcq2021/03/18 06:30 AM
                                  Microkernel?dmcq2021/03/18 06:55 AM
                                  Microkernel?Adrian2021/03/18 08:35 AM
                                    Microkernel?---2021/03/18 09:49 AM
                                    Microkernel?dmcq2021/03/18 10:59 AM
                                      Microkernel?dmcq2021/03/18 04:09 PM
                              Microkernel?---2021/03/18 09:27 AM
                          Microkernel?Kalle A. Sandström2021/03/20 06:34 AM
                            Microkernel?---2021/03/20 08:35 AM
                            Microkernel?anon22021/03/21 05:29 PM
            Microkernel?dmcq2021/03/15 04:06 AM
              Microkernel?anon22021/03/15 04:59 AM
                Microkernel?dmcq2021/03/15 11:51 AM
                  Microkernel?anon22021/03/15 08:31 PM
                    Microkernel?dmcq2021/03/16 09:17 AM
                      Microkernel?Jukka Larja2021/03/16 11:22 AM
                        Microkernel?dmcq2021/03/16 04:06 PM
                          Microkernel?Jukka Larja2021/03/17 03:42 AM
                            Microkernel?dmcq2021/03/17 07:00 AM
                      Microkernel?anon22021/03/16 05:26 PM
                    Microkernel?---2021/03/16 10:07 AM
            Microkernel?-.-2021/03/15 08:15 PM
              Microkernel?anon22021/03/15 09:18 PM
                Microkernel?Foo_2021/03/16 03:37 AM
                  Read the thread (NT)anon22021/03/16 05:27 PM
                    Already did (NT)Foo_2021/03/17 02:55 AM
                      Already didanon22021/03/17 03:46 AM
                        Already didEtienne Lorrain2021/03/18 02:31 AM
                Microkernel?-.-2021/03/17 05:04 AM
                  Microkernel?Gabriele Svelto2021/03/17 08:53 AM
                    Microkernel?-.-2021/03/17 02:43 PM
              Microkernel?dmcq2021/03/16 08:40 AM
        x86 - why unite when you can fragment?Konrad Schwarz2021/03/17 10:19 AM
    x86 - why unite when you can fragment?anonon2021/03/15 07:37 AM
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