[PATCH] KVM: PPC: Book3S HV: Treat unrecognized TM instructions as illegal

[Gustavo Romero]

Hi,

On 02/17/2020 04:37 AM, Segher Boessenkool wrote:
> On Mon, Feb 17, 2020 at 05:23:07PM +1100, Michael Neuling wrote:
>>>> Hence, we should NOP this, not generate an illegal.
>>>
>>> It is not a reserved bit.
>>>
>>> The IMC entry for it matches op1=011111 op2=1////01110 presumably, which
>>> catches all TM instructions and nothing else (bits 0..5 and bits 21..30).
>>> That does not look at bit 31, the softpatch handler has to deal with this.
>>>
>>> Some TM insns have bit 31 as 1 and some have it as /.  All instructions
>>> with a "." in the mnemonic have bit 31 is 1, all other have it reserved.
>>> The tables in appendices D, E, F show tend. and tsr. as having it
>>> reserved, which contradicts the individual instruction description (and
>>> does not make much sense).  (Only tcheck has /, everything else has 1;
>>> everything else has a mnemonic with a dot, and does write CR0 always).
>>
>> Wow, interesting.
>>
>> P8 seems to be treating 31 as a reserved bit (with the table definition rather
>> than the individual instruction description). I'm inclined to match P8 even
>> though it's inconsistent with the dot mnemonic as you say.
> 
> "The POWER8 core ignores the state of reserved bits in the instructions
> (denoted by “///” in the instruction definition) and executes the
> instruction normally. Software should set these bits to ‘0’ per the
> Power ISA." (p8 UM, 3.1.1.3; same in the p9 UM).

For the records, I've sent a v2 addressing Mikey's comments:

https://lists.ozlabs.org/pipermail/linuxppc-dev/2020-February/204502.html

or

https://marc.info/?l=kvm-ppc&m=158206045520038&w=2

Thanks for the review.


Best regards,
Gustavo