Re: [PATCH 8/9] target/ppc: Introduce a vhyp framework for nested HV support

[Fabiano Rosas <farosas@linux.ibm.com>]

Nicholas Piggin <npiggin@gmail.com> writes:

> Introduce virtual hypervisor methods that can support a "Nested KVM HV"
> implementation using the bare metal 2-level radix MMU, and using HV
> exceptions to return from H_ENTER_NESTED (rather than cause interrupts).
>
> HV exceptions can now be raised in the TCG spapr machine when running a
> nested KVM HV guest. The main ones are the lev==1 syscall, the hdecr,
> hdsi and hisi, hv fu, and hv emu, and h_virt external interrupts.
>
> HV exceptions are intercepted in the exception handler code and instead
> of causing interrupts in the guest and switching the machine to HV mode,
> they go to the vhyp where it may exit the H_ENTER_NESTED hcall with the
> interrupt vector numer as return value as required by the hcall API.
>
> Address translation is provided by the 2-level page table walker that is
> implemented for the bare metal radix MMU. The partition scope page table
> is pointed to the L1's partition scope by the get_pate vhc method.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>