Re: [PATCH] KVM: arm64: nv: Forward hvc traps if originated from nested VM

[Marc Zyngier]

On Thu, 10 Apr 2025 08:07:43 +0100,
Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> 
> It was discovered while trying selftest(smccc_filter) that the
> hvc trap is getting forwarded to guest hypervisor even if it is
> originated from itself.
> 
> HVC traps from guest hypervisor should be handled by the host
> hypervisor and traps originating from nested VM should be
> forwarded. Adding check to forward only if the hvc is trapped
> from the nested VM.

I disagree. HVC from EL2 must be routed to the same EL2. HVC from EL1
must be routed to the EL2 controlling EL1.

In no circumstances should HVC from a NV guest be directly handled by
the host hypervisor. That's what SMC is for.

Please read the pseudocode for HVC.

	M.

-- 
Without deviation from the norm, progress is not possible.