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