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  • Virtualization layers (was: Constant Stack Canaries)

    From Stefan Monnier@21:1/5 to All on Wed Apr 16 17:48:49 2025
    Given 4 layers in the stack {Secure, Hyper, Super, User} and we have interrupts targeting {Secure, Hyper, Super}, do we pick up any liability
    or do we gain flexibility by being able to target interrupts directly to {user} ?? (the 4th element).

    All these discussions seem to presume a very fixed structure that (I
    presume) corresponds to a typical situation in servers nowadays.

    But shouldn't the hardware aim for something more flexible to account
    for other use cases?

    E.g. What if I want to run my own VM as a user? Or my own HV?
    That's likely to be a common desire for people working on the
    development and testing of OSes and HVs?


    Stefan

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  • From MitchAlsup1@21:1/5 to Stefan Monnier on Wed Apr 16 22:12:22 2025
    On Wed, 16 Apr 2025 21:48:49 +0000, Stefan Monnier wrote:

    Given 4 layers in the stack {Secure, Hyper, Super, User} and we have
    interrupts targeting {Secure, Hyper, Super}, do we pick up any liability
    or do we gain flexibility by being able to target interrupts directly to
    {user} ?? (the 4th element).

    All these discussions seem to presume a very fixed structure that (I
    presume) corresponds to a typical situation in servers nowadays.

    But shouldn't the hardware aim for something more flexible to account
    for other use cases?

    The goal is that::
    The two layers in the middle can be managed as an accordion; supporting
    any number of HVs and GuestOSs between Secure and User.

    E.g. What if I want to run my own VM as a user? Or my own HV?
    That's likely to be a common desire for people working on the
    development and testing of OSes and HVs?

    Use the accordion


    Stefan

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  • From Scott Lurndal@21:1/5 to Stefan Monnier on Thu Apr 17 00:49:37 2025
    Stefan Monnier <monnier@iro.umontreal.ca> writes:
    Given 4 layers in the stack {Secure, Hyper, Super, User} and we have
    interrupts targeting {Secure, Hyper, Super}, do we pick up any liability
    or do we gain flexibility by being able to target interrupts directly to
    {user} ?? (the 4th element).

    All these discussions seem to presume a very fixed structure that (I
    presume) corresponds to a typical situation in servers nowadays.

    But shouldn't the hardware aim for something more flexible to account
    for other use cases?

    E.g. What if I want to run my own VM as a user? Or my own HV?
    That's likely to be a common desire for people working on the
    development and testing of OSes and HVs?

    ARM has hardware support for nested hypervisors. It can be tricky.

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