[PATCH v4 03/40] KVM: arm64: Avoid storing the vcpu pointer on the stack

[Julien Grall]

Hi Christoffer,

On 15/02/18 21:02, Christoffer Dall wrote:
> We already have the percpu area for the host cpu state, which points to
> the VCPU, so there's no need to store the VCPU pointer on the stack on
> every context switch.  We can be a little more clever and just use
> tpidr_el2 for the percpu offset and load the VCPU pointer from the host
> context.
> 
> This does require us to calculate the percpu offset without including
> the offset from the kernel mapping of the percpu array to the linear
> mapping of the array (which is what we store in tpidr_el1), because a
> PC-relative generated address in EL2 is already giving us the hyp alias
> of the linear mapping of a kernel address.  We do this in
> __cpu_init_hyp_mode() by using kvm_ksym_ref().
> 
> This change also requires us to have a scratch register, so we take the
> chance to rearrange some of the el1_sync code to only look at the
> vttbr_el2 to determine if this is a trap from the guest or an HVC from
> the host.  We do add an extra check to call the panic code if the kernel
> is configured with debugging enabled and we saw a trap from the host
> which wasn't an HVC, indicating that we left some EL2 trap configured by
> mistake.

You might want to remove this paragraph as you don't seem to have rework 
that part of the code in this version.

Cheers,

-- 
Julien Grall