Re: [PATCH] KVM: arm64: Clarify vcpu reset behaviour

[Marc Zyngier <maz@kernel.org>]

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@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.

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

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

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