[9fans] From our "not quite grasping the concept" file - Plan9

This is a discussion on [9fans] From our "not quite grasping the concept" file - Plan9 ; I offer this: http://groups.google.com/group/fa.li...bd004?lnk=raot "I dislike strings. They make it look as if you have a nice extensible interface, where in reality you have a poorly documented interface which leads to poor interoperability." So, the decision in the linux virtualization ...

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  1. [9fans] From our "not quite grasping the concept" file

    I offer this:
    http://groups.google.com/group/fa.li...bd004?lnk=raot

    "I dislike strings. They make it look as if you have a nice extensible
    interface, where in reality you have a poorly documented interface which
    leads to poor interoperability."

    So, the decision in the linux virtualization world is to make all
    paravirtual devices look like ... drum roll ... PCI devices. Since, of
    course, PCI device is the Universal device.

    My brain hurts.

    ron

  2. Re: [9fans] From our "not quite grasping the concept" file

    > So, the decision in the linux virtualization world is to make all
    > paravirtual devices look like ... drum roll ... PCI devices.


    That's really tragic. Virtualisation of devices would be such a good
    opportunity to invent a nice simple interface abstracting away from
    all the hardware constraints. Sure, all the guest OSs will need new
    drivers - but using a simple interface means they should be really
    easy to write.


  3. Re: [9fans] From our "not quite grasping the concept" file

    On Nov 8, 2007 6:00 AM, Richard Miller <9fans@hamnavoe.com> wrote:
    > > So, the decision in the linux virtualization world is to make all
    > > paravirtual devices look like ... drum roll ... PCI devices.

    >
    > That's really tragic. Virtualisation of devices would be such a good
    > opportunity to invent a nice simple interface abstracting away from
    > all the hardware constraints. Sure, all the guest OSs will need new
    > drivers - but using a simple interface means they should be really
    > easy to write.
    >


    The opportunity still exists -- only one driver needs to implement
    their numeric hack - 9p. Then the rest can be based off of that.
    Unfortunately, evolution just comes slow and painful.

    -eric

  4. Re: [9fans] From our "not quite grasping the concept" file

    >> So, the decision in the linux virtualization world is to make all
    >> paravirtual devices look like ... drum roll ... PCI devices.

    >
    > That's really tragic. Virtualisation of devices would be such a good
    > opportunity to invent a nice simple interface abstracting away from
    > all the hardware constraints. Sure, all the guest OSs will need new
    > drivers - but using a simple interface means they should be really
    > easy to write.


    one day software will break
    free of this silicon coil
    the code will then ache
    for one more cycle to toil

    - erik


  5. Re: [9fans] From our "not quite grasping the concept" file

    > The opportunity still exists -- only one driver needs to implement
    > their numeric hack - 9p. Then the rest can be based off of that.
    > Unfortunately, evolution just comes slow and painful.
    >
    > -eric


    are 9p mesages really the right vehicle for this? 9p messages
    provides a serialized and in a standard byte order. this requires
    byte reordering (on intel) and copying. but are these really needed?
    the guest and host are on the same platform, so the guest can
    pass pointers to the host. for the same reason, integers don't need
    reformatting.

    modern devices usually dma directly, so the host may never need
    to touch the pointed-to memory.

    perhaps using Fcall structures directly would be more efficient?

    - erik


  6. Re: [9fans] From our "not quite grasping the concept" file


    On Nov 8, 2007, at 8:20 AM, erik quanstrom wrote:

    >> The opportunity still exists -- only one driver needs to implement
    >> their numeric hack - 9p. Then the rest can be based off of that.
    >> Unfortunately, evolution just comes slow and painful.
    >>
    >> -eric

    >
    > are 9p mesages really the right vehicle for this? 9p messages
    > provides a serialized and in a standard byte order. this requires
    > byte reordering (on intel) and copying. but are these really needed?
    > the guest and host are on the same platform, so the guest can
    > pass pointers to the host. for the same reason, integers don't need
    > reformatting.
    >
    > modern devices usually dma directly, so the host may never need
    > to touch the pointed-to memory.
    >
    > perhaps using Fcall structures directly would be more efficient?


    That's one of the options. We are probably going to start with
    serialized content (no copying of the data though) and if it is too
    slow, we won't do serialization.

    Thanks,
    Lucho

  7. Re: [9fans] From our "not quite grasping the concept" file

    On Nov 8, 2007 9:20 AM, erik quanstrom wrote:
    > > The opportunity still exists -- only one driver needs to implement
    > > their numeric hack - 9p. Then the rest can be based off of that.
    > > Unfortunately, evolution just comes slow and painful.
    > >
    > > -eric

    >
    > are 9p mesages really the right vehicle for this? 9p messages
    > provides a serialized and in a standard byte order. this requires
    > byte reordering (on intel) and copying. but are these really needed?
    > the guest and host are on the same platform, so the guest can
    > pass pointers to the host. for the same reason, integers don't need
    > reformatting.
    >


    9p is the right organizational structure. The details of marshalling
    and pass-by-copy versus pass-by-reference are transport issues. Lucho
    and I have been playing with zero-marhsalling/zero-copy transport
    variants of 9P for virtualized environments.

    -eric

  8. Re: [9fans] From our "not quite grasping the concept" file

    > > are 9p mesages really the right vehicle for this? 9p messages
    > > provides a serialized and in a standard byte order. this requires
    > > byte reordering (on intel) and copying. but are these really needed?
    > > the guest and host are on the same platform, so the guest can
    > > pass pointers to the host. for the same reason, integers don't need
    > > reformatting.
    > >

    >
    > 9p is the right organizational structure. The details of marshalling
    > and pass-by-copy versus pass-by-reference are transport issues. Lucho
    > and I have been playing with zero-marhsalling/zero-copy transport
    > variants of 9P for virtualized environments.
    >
    > -eric


    perhaps i'm being too pedantic, but 9p is defined by how it marshals data.

    - erik

  9. Re: [9fans] From our "not quite grasping the concept" file

    > That's one of the options. We are probably going to start with
    > serialized content (no copying of the data though) and if it is too
    > slow, we won't do serialization.


    i'm not sure i understand. either the message is formatted (and the data
    copied) or it's not. i must be missing something.

    - erik

  10. Re: [9fans] From our "not quite grasping the concept" file

    On Nov 8, 2007 8:33 AM, erik quanstrom wrote:
    > > > are 9p mesages really the right vehicle for this? 9p messages
    > > > provides a serialized and in a standard byte order. this requires
    > > > byte reordering (on intel) and copying. but are these really needed?
    > > > the guest and host are on the same platform, so the guest can
    > > > pass pointers to the host. for the same reason, integers don't need
    > > > reformatting.
    > > >

    > >
    > > 9p is the right organizational structure. The details of marshalling
    > > and pass-by-copy versus pass-by-reference are transport issues. Lucho
    > > and I have been playing with zero-marhsalling/zero-copy transport
    > > variants of 9P for virtualized environments.
    > >
    > > -eric

    >
    > perhaps i'm being too pedantic, but 9p is defined by how it marshals data.



    You guys lost me. The header fields are in a certain byte order, but
    when did the data start being byte-reordered? Have I been missing this
    reordering all these years? I sure never implemented it in my code ...
    which worked fine between Alpha and x86.

    ron

  11. Re: [9fans] From our "not quite grasping the concept" file

    > this requires byte reordering (on intel)

    sorry to be pedantic, but 9p uses little-endian integers
    so it's the big-endian machines that need to do byte reordering.

  12. Re: [9fans] From our "not quite grasping the concept" file

    It is not necessary the message to be in a single block of memory.
    The message header can be prepared in one block and the rest of the
    data can be in a different one. As Eric said, all this is transport
    specific.

    Lucho

    On Nov 8, 2007, at 9:38 AM, erik quanstrom wrote:

    >> That's one of the options. We are probably going to start with
    >> serialized content (no copying of the data though) and if it is too
    >> slow, we won't do serialization.

    >
    > i'm not sure i understand. either the message is formatted (and
    > the data
    > copied) or it's not. i must be missing something.
    >
    > - erik



  13. Re: [9fans] From our "not quite grasping the concept" file

    Here's a question: What do strings have to do with PCI devices? Don't
    ID tags end with \0 or something?

    On Nov 8, 2007, at 2:31 AM, ron minnich wrote:

    > I offer this:
    > http://groups.google.com/group/fa.li...thread/thread/
    > 5f92fd9fa6c2c64f/ef69521d8d0bd004?lnk=raot
    >
    > "I dislike strings. They make it look as if you have a nice
    > extensible
    > interface, where in reality you have a poorly documented interface
    > which
    > leads to poor interoperability."
    >
    > So, the decision in the linux virtualization world is to make all
    > paravirtual devices look like ... drum roll ... PCI devices. Since, of
    > course, PCI device is the Universal device.
    >
    > My brain hurts.
    >
    > ron



  14. Re: [9fans] From our "not quite grasping the concept" file

    What's really bizarre is that, if you read on,
    it says
    "PCI means that you can reuse all of the platform's infrastructure for
    irq allocation, discovery, device hotplug, and management."

    i.e. mandates 386 style interrupt handling.

    Even better:
    "We will support non-pci for s390, but in order to support Windows and
    older Linux PCI is necessary."

    WTF? So this "virtual device" concept only works on either PCI-w/386-
    style-interrupts or s390 machines?

    Is it just me or is the whole linux universe stark raving bonkers?

    What does the PCI bus on a mobile phone look like?

    DaveL

    On 8 Nov 2007, at 07:31, ron minnich wrote:

    > I offer this:
    > http://groups.google.com/group/fa.li...thread/thread/
    > 5f92fd9fa6c2c64f/ef69521d8d0bd004?lnk=raot
    >
    > "I dislike strings. They make it look as if you have a nice
    > extensible
    > interface, where in reality you have a poorly documented interface
    > which
    > leads to poor interoperability."
    >
    > So, the decision in the linux virtualization world is to make all
    > paravirtual devices look like ... drum roll ... PCI devices. Since, of
    > course, PCI device is the Universal device.
    >
    > My brain hurts.
    >
    > ron



  15. Re: [9fans] From our "not quite grasping the concept" file

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    On 8-Nov-07, at 5:07 PM, dave.l@mac.com wrote:
    > Is it just me or is the whole linux universe stark raving bonkers?


    Insular is the word you're looking for.

    Paul

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