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Re: [PATCH 9/9] spapr: implement nested-hv capability for the virtual hy

From: Fabiano Rosas
Subject: Re: [PATCH 9/9] spapr: implement nested-hv capability for the virtual hypervisor
Date: Tue, 15 Feb 2022 13:01:38 -0300

Nicholas Piggin <npiggin@gmail.com> writes:

> This implements the Nested KVM HV hcall API for spapr under TCG.
> The L2 is switched in when the H_ENTER_NESTED hcall is made, and the
> L1 is switched back in returned from the hcall when a HV exception
> is sent to the vhyp. Register state is copied in and out according to
> the nested KVM HV hcall API specification.
> The hdecr timer is started when the L2 is switched in, and it provides
> the HDEC / 0x980 return to L1.
> The MMU re-uses the bare metal radix 2-level page table walker by
> using the get_pate method to point the MMU to the nested partition
> table entry. MMU faults due to partition scope errors raise HV
> exceptions and accordingly are routed back to the L1.
> The MMU does not tag translations for the L1 (direct) vs L2 (nested)
> guests, so the TLB is flushed on any L1<->L2 transition (hcall entry
> and exit).
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

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

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