Re: [Qemu-devel] [PATCH for-2.11?] target/arm: Generate UNDEF for 32-bit Thumb2 insns

[Peter Maydell <peter.maydell@linaro.org>]

On 11 December 2017 at 17:00, Richard Henderson <rth@twiddle.net> wrote:
> On 12/11/2017 07:42 AM, Peter Maydell wrote:
>> The refactoring of commit 296e5a0a6c3935 has a nasty bug:
>> it accidentally dropped the generation of code to raise
>> the UNDEF exception when disas_thumb2_insn() returns nonzero.
>> This means that 32-bit Thumb2 instruction patterns that
>> ought to UNDEF just act like nops instead. This is likely
>> to break any number of things, including the kernel's "disable
>> the FPU and use the UNDEF exception to identify when to turn
>> it back on again" trick.
>>
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> ---
>> This is the smallest possible fix that will correct the
>> bug, for possible inclusion in 2.11; for 2.12 we should
>> fix the asymmetry where disas_thumb() generates its own
>> exception-raising code but disas_thumb2() wants the caller
>> to do it. (This asymmetry is why we didn't notice the
>> problem in code review.)
>>
>> I'm not sure whether this should go into 2.11 or not --
>> this time last week it would have been an easy "yes".
>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Thanks. I think I have come down on the side of putting this into
2.11, so rolling an rc5 today, and delaying the final release
a day to Wednesday.

thanks
-- PMM