[PATCH] KVM: arm64: Clarify vcpu reset behaviour

[Will Deacon]

On Thu, Apr 08, 2021 at 11:36:34AM +0100, Marc Zyngier wrote:
> On 2021-04-07 21:35, Will Deacon wrote:
> > On Tue, Apr 06, 2021 at 01:58:41PM +0100, Marc Zyngier wrote:
> > > Although the KVM_ARM_VCPU_INIT documentation mention that the
> > > registers are reset to their "initial values", it doesn't
> > > describe what these values are.
> > > 
> > > Describe this state explicitly.
> > > 
> > > Signed-off-by: Marc Zyngier <maz at kernel.org>
> > > ---
> > >  Documentation/virt/kvm/api.rst | 10 ++++++++++
> > >  1 file changed, 10 insertions(+)
> > > 
> > > diff --git a/Documentation/virt/kvm/api.rst
> > > b/Documentation/virt/kvm/api.rst
> > > index 38e327d4b479..e2237e4e10ba 100644
> > > --- a/Documentation/virt/kvm/api.rst
> > > +++ b/Documentation/virt/kvm/api.rst
> > > @@ -3115,6 +3115,16 @@ optional features it should have.  This will
> > > cause a reset of the cpu
> > >  registers to their initial values.  If this is not called, KVM_RUN
> > > will
> > >  return ENOEXEC for that vcpu.
> > > 
> > > +The initial values are defined as:
> > > +	- Processor state:
> > > +		* AArch64: EL1h, D, A, I and F bits set
> > > +		* Aarch32: SVC, D, A, I and F bits set
> > 
> > nit, but capitalisation should be "AArch32"
> > 
> > Is "SVC" sufficient, or do we also need to describe Arm vs Thumb?
> 
> SVC doesn't describe the instruction set, but we don't say that PSR.T
> is set, which implies ARM.

Ah yes, thanks.

> I can add something like "All other bits are set to 0", if that makes it
> clearer.

I think that would be worth adding. With that and the minor typo fix:

Acked-by: Will Deacon <will at kernel.org>

Will