Re: [Qemu-devel] [PATCH v3 3/6] target-arm: add hvc and smc exception emulation handling infrastructure

[Peter Maydell]

On 9 September 2014 22:51, Ard Biesheuvel <address@hidden> wrote:
> On 9 September 2014 19:45, Peter Maydell <address@hidden> wrote:
>> This is my suggestion for the best compromise between
>> "theoretical perfect fidelity to the architecture" and
>> "not too painful to implement":
>> at translate time, do:
>>
>>   if (psci enabled via HVC || EL2 implemented) {
>>       gen_ss_advance(s);
>>       gen_exception_insn(s, 0, EXCP_HVC, syn_aa64_hvc(imm16));
>>   } else {
>>       unallocated_encoding();
>>   }
>> and ditto for SMC.
>>
>
> OK, so does that mean I need to add fields to DisasContext for these
> functions to inspect at the translation stage, and copy the
> PSCI_METHOD_[SVC|HVC|NONE] values in it?

You only need one field in DisasContext, but yes.
(The idea of DisasContext and not giving most of translate-a64.c
access to the CPU object is that it makes it hard to accidentally
access stuff in the CPU object that's not valid to depend on at
translate time, because it's an easy to spot and easy to review
change if something new gets added. PSCI method type is
OK because it's constant for the life of the simulation.)

> Yeah, makes sense. I will also add ARCH(6K) and ARCH(7) checks, for
> SMC and HVC respectively.
> (I don't suppose there is any point in adding TZ and VIRT feature bits
> for this atm)

We already have ARM_FEATURE_EL2 and ARM_FEATURE_EL3,
actually. You should probably look at Edgar's patchset on list which
adds proper SMC/HVC support -- that has failed review on a
few of the early patches but the middle of the set includes
some which also change this area:
http://lists.gnu.org/archive/html/qemu-devel/2014-08/msg02865.html
http://lists.gnu.org/archive/html/qemu-devel/2014-08/msg02866.html
I don't want this patchset to depend on that one but you
might find the shape of the code useful. (It doesn't do anything
in the 32 bit code, though.)

thanks
-- PMM