On Mon, 2011-05-09 at 16:31 +0100, Hollis Blanchard wrote:
> On Sun, May 8, 2011 at 7:00 AM, Christoffer Dall <cdall at cs.columbia.edu> wrote:
> > This patch contains the KVM code including the simple version of the
> > initialization API that we discussed.
>
> I missed the discussion, so I'm not really sure what the context is,
> but just a quick question:
That was some private discussion around getting the Linux KVM to execute
some code in Hypervisor mode on ARM processors with such extension
(Cortex-A15).
> > +/*
> > + * Change the current processor mode to Hyp mode.
> > + * You should never return to user space or enable interrupts before calling
> > + * kvm_arm_hyp_return.
> > + */
> > +static inline void kvm_arm_hyp_mode(void)
> > +{
> > + __asm__ (
> > + "push {lr}\n\t"
> > + "hvc #0\n\t"
> > + "pop {lr}\n\t");
> > +}
> > +
> > +/*
> > + * Return from Hyp mode to Svc mode.
> > + */
> > +static inline void kvm_arm_hyp_return(void)
> > +{
> > + __asm__ (
> > + "push {lr}\n\t"
> > + "hvc #0\n\t"
> > + "pop {lr}\n\t");
> > +}
>
> Are these hypercalls that return in a new processor privilege level?
> (Also, I don't see them being used anywhere.)
The HVC makes the switch to the Hypervisor mode (similar to how SVC
switches from User to Supervisor mode).
> Is the A15 ISA documentation available anywhere yet?
The A15 consists of the standard ARMv7 ISA plus the virtualisation
extensions. These are described in:
http://infocenter.arm.com/help/topic/com.arm.doc.ddi0406b_virtualization_extns/index.html
(they are free to access with a click-through license)
--
Catalin
