[PATCH 0/3] target/arm: More HCR_EL2.TIDx fixes

Marc Zyngier posted 3 patches 2 weeks ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/20191128161718.24361-1-maz@kernel.org
Maintainers: Peter Maydell <peter.maydell@linaro.org>
target/arm/helper-a64.h        |  2 ++
target/arm/helper.c            | 64 ++++++++++++++++++++++++++++++----
target/arm/internals.h         |  8 +++++
target/arm/translate-vfp.inc.c | 12 +++++--
target/arm/vfp_helper.c        | 27 ++++++++++++++
5 files changed, 103 insertions(+), 10 deletions(-)

[PATCH 0/3] target/arm: More HCR_EL2.TIDx fixes

Posted by Marc Zyngier 2 weeks ago
I started looking the rest of the missing TIDx handling,
and this resulted in the following patches.

There is still one thing I'm a bit puzzled by though:

HCR_EL2.TID0 mandates trapping of the AArch32 JIDR
register, but I couldn't find a trace of it in the QEMU
code, and trying to read it seems to generate an exception.

It isn't like anyone is going to miss it, but I wonder if
it should be implemented... It could also be that I'm missing
the obvious and that my testing is broken! ;-)

Marc Zyngier (3):
  target/arm: Honor HCR_EL2.TID2 trapping requirements
  target/arm: Honor HCR_EL2.TID1 trapping requirements
  target/arm: Handle trapping to EL2 of AArch32 VMRS instructions

 target/arm/helper-a64.h        |  2 ++
 target/arm/helper.c            | 64 ++++++++++++++++++++++++++++++----
 target/arm/internals.h         |  8 +++++
 target/arm/translate-vfp.inc.c | 12 +++++--
 target/arm/vfp_helper.c        | 27 ++++++++++++++
 5 files changed, 103 insertions(+), 10 deletions(-)

-- 
2.20.1


Re: [PATCH 0/3] target/arm: More HCR_EL2.TIDx fixes

Posted by Peter Maydell 2 weeks ago
On Thu, 28 Nov 2019 at 16:17, Marc Zyngier <maz@kernel.org> wrote:
>
> I started looking the rest of the missing TIDx handling,
> and this resulted in the following patches.
>
> There is still one thing I'm a bit puzzled by though:
>
> HCR_EL2.TID0 mandates trapping of the AArch32 JIDR
> register, but I couldn't find a trace of it in the QEMU
> code, and trying to read it seems to generate an exception.
>
> It isn't like anyone is going to miss it, but I wonder if
> it should be implemented... It could also be that I'm missing
> the obvious and that my testing is broken! ;-)

Hmm, I was under the impression that we correctly implemented
'trivial Jazelle', but we obviously missed some of it
(we do have the handling of BXJ insns).
We should, yes, ideally, have RAZ/WI implementations
of JIDR, JMCR and JOSCR.

We also I think don't get right the fiddly detail about
attempting an exception return with SPSR.J set, but that's
not worth messing about with IMHO.

thanks
-- PMM

Re: [PATCH 0/3] target/arm: More HCR_EL2.TIDx fixes

Posted by Marc Zyngier 2 weeks ago
On 2019-11-28 16:30, Peter Maydell wrote:
> On Thu, 28 Nov 2019 at 16:17, Marc Zyngier <maz@kernel.org> wrote:
>>
>> I started looking the rest of the missing TIDx handling,
>> and this resulted in the following patches.
>>
>> There is still one thing I'm a bit puzzled by though:
>>
>> HCR_EL2.TID0 mandates trapping of the AArch32 JIDR
>> register, but I couldn't find a trace of it in the QEMU
>> code, and trying to read it seems to generate an exception.
>>
>> It isn't like anyone is going to miss it, but I wonder if
>> it should be implemented... It could also be that I'm missing
>> the obvious and that my testing is broken! ;-)
>
> Hmm, I was under the impression that we correctly implemented
> 'trivial Jazelle', but we obviously missed some of it
> (we do have the handling of BXJ insns).
> We should, yes, ideally, have RAZ/WI implementations
> of JIDR, JMCR and JOSCR.

OK, I'll have a look at this, and plumb the handling of TID0
in JIDR.

> We also I think don't get right the fiddly detail about
> attempting an exception return with SPSR.J set, but that's
> not worth messing about with IMHO.

Indeed. The less we hear about Jazelle, the better... ;-)

Thanks,

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