[PATCH v2 05/13] KVM: arm64: Restore mdcr_el2 from vcpu

[Fuad Tabba]

Hi Will,

On Thu, Jul 1, 2021 at 2:17 PM Will Deacon <will at kernel.org> wrote:
>
> On Tue, Jun 15, 2021 at 02:39:42PM +0100, Fuad Tabba wrote:
> > On deactivating traps, restore the value of mdcr_el2 from the
> > vcpu context, rather than directly reading the hardware register.
> > Currently, the two values are the same, i.e., the hardware
> > register and the vcpu one. A future patch will be changing the
> > value of mdcr_el2 on activating traps, and this ensures that its
> > value will be restored.
> >
> > No functional change intended.
> >
> > Signed-off-by: Fuad Tabba <tabba at google.com>
> > ---
> >  arch/arm64/kvm/hyp/nvhe/switch.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
> > index f7af9688c1f7..430b5bae8761 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/switch.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/switch.c
> > @@ -73,7 +73,7 @@ static void __deactivate_traps(struct kvm_vcpu *vcpu)
> >
> >       ___deactivate_traps(vcpu);
> >
> > -     mdcr_el2 = read_sysreg(mdcr_el2);
> > +     mdcr_el2 = vcpu->arch.mdcr_el2;
>
> Do you need to change the VHE code too?

No. The code that would toggle mdcr_el2 only affects nvhe and only in
protected mode.

Cheers,
/fuad

>
> Will