[PATCH v4 00/28] arm/arm64: KVM: Rework the hyp-stub API
Marc Zyngier
marc.zyngier at arm.com
Wed Mar 22 09:14:44 PDT 2017
Hi Christoffer,
On 22/03/17 13:37, Christoffer Dall wrote:
> Hi Marc,
>
>
> On Tue, Mar 21, 2017 at 07:20:30PM +0000, Marc Zyngier wrote:
>> As noticed by RMK in this thread[1], the hyp-stub API on 32bit ARM
>> could do with some TLC (it cannot perform a soft-restart at HYP, and
>> has holes in the hyp-stub support in a number of places). In general,
>> it would be desirable for the 32bit behaviour to align on 64bit, if
>> only to ease maintenance.
>>
>> This series implements the following:
>> - Add HVC_[GS]ET_VECTORS and HVC_SOFT_RESTART to the 32bit code
>> - Add HVC_RESET_VECTORS to both arm and arm64, removing the need for
>> __hyp_reset_vectors
>> - Implement add the stub entry points in the KVM init code, which
>> didn't implement any so far
>> - Convert the HYP code to use the init code stubs directly
>> - Some general cleanup as a result of these changes (which includes
>> killing HVC_GET_VECTORS)
>> - Add some API documentation that covers the above
>>
>> Patches 12 to 14 would be better squashed into 10 and 11, but I've
>> kept them separate so that I can take the blame for everything I've
>> broken.
>
> This series looks great overall. I'm still going through the details of
> the patches, but one high level questions:
>
> What if we formalized the way to call a function in Hyp mode, whatever
> its current configuration may be, via a specific HVC number. That would
> mean that the documentation say nothing of a hypervisor specific
> implementaiton.
Do you mean an actual function call indirected via an HVC? Similar to
what we already do today for KVM when we want to call HYP functions?
> Could we then use that to initialize hyp mode for a hypervisor, i.e.
> KVM, without having to actually change the vectors? Couldn't we simply
> use the the hvc stub to call a function in the physical address space,
> and be rid of the concept of hyp-init alltogether?
My problem here is when you say "in the physical space". Do you want to
be able to call such a function from any context? That's certainly
doable now, but I'm not completely sure of what we get.
Maybe I just don't see the use case - can you enlighten me?
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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