[PATCH v4 15/46] KVM: PPC: Book3S 64: Move hcall early register setup to KVM

[Nicholas Piggin]

Excerpts from Paul Mackerras's message of April 1, 2021 3:41 pm:
> On Tue, Mar 23, 2021 at 11:02:34AM +1000, Nicholas Piggin wrote:
>> System calls / hcalls have a different calling convention than
>> other interrupts, so there is code in the KVMTEST to massage these
>> into the same form as other interrupt handlers.
>> 
>> Move this work into the KVM hcall handler. This means teaching KVM
>> a little more about the low level interrupt handler setup, PACA save
>> areas, etc., although that's not obviously worse than the current
>> approach of coming up with an entirely different interrupt register
>> / save convention.
> 
> [snip]
> 
>> @@ -1964,29 +1948,8 @@ EXC_VIRT_END(system_call, 0x4c00, 0x100)
>>  
>>  #ifdef CONFIG_KVM_BOOK3S_64_HANDLER
>>  TRAMP_REAL_BEGIN(system_call_kvm)
>> -	/*
>> -	 * This is a hcall, so register convention is as above, with these
>> -	 * differences:
> 
> I haven't checked all the code changes in detail yet, but this comment
> at least is slightly misleading, since under PR KVM, system calls (to
> the guest kernel) and hypercalls both come through this path.

Yeah good point, I'll update the comment at its destination.

Thanks,
Nick