Re: [RFC PATCH v3 0/3] Implement Power ISA 3.1B hash insns

["Víctor Colombo" <victor.colombo@eldorado.org.br>]

On 15/07/2022 10:23, Daniel Henrique Barboza wrote:
> On 7/13/22 13:54, Víctor Colombo wrote:
>> This patch series implements the 4 instructions added in Power ISA
>> 3.1B:
>>
>> - hashchk
>> - hashst
>> - hashchkp
>> - hashstp
>>
>> To build it, you need to apply the following patches on top of master:
>> <20220701133507.740619-2-lucas.coutinho@eldorado.org.br>
>> <20220701133507.740619-3-lucas.coutinho@eldorado.org.br>
>> <20220712193741.59134-2-leandro.lupori@eldorado.org.br>
>> <20220712193741.59134-3-leandro.lupori@eldorado.org.br>
>>
>> Working branch for ease of use can be found here:
>> https://github.com/PPC64/qemu/tree/vccolombo-hash-to-send-v3
>>
>> What do you think about the choice to implement the hash algorithm
>> from the ground up, following the SIMON-like algorithm presented in
>> Power ISA? IIUC, this algorithm is not the same as the original[1].
>> Other options would be to use other algorithm already implemented
>> in QEMU, or even make this instruction a nop for all Power versions.
>>
>> Also, I was thinking about using the call to spr_register_kvm() in
>> init_proc_POWER10 to initialize the registers with a random value.
>> I'm not sure what is the behavior here, I would expect that is the job
>> of the OS to set the regs, but looks like KVM is not exporting them,
>> so they are always 0 (?). Does anyone have any insight on this?
> 
> This happens because KVM on POWER10 isn't handling these registers
> appropriately. We are probably missing kernel/kvm code to do so.
> 
> Since KVM on POWER10 is on an uncertain spot at this moment I wouldn't
> worry too much about it. Making the regs read/write work in TCG is good
> enough for now.
> 
> 
> Daniel

Hello Daniel,

Thanks for taking a look at this. I agree that in this case it is better
to make it work in TCG and drop the KVM part from this patch set
I'll work on it now

Thanks!

> 
>>
>> v1->v2:
>> - Split the patch in 2
>> - Rebase to master
>>
>> v2->v3:
>> - Split patches in 3
>>      - the new patch (patch 1) is separating the kvm header
>>        changes [Cornelia]
>>
>> [1] https://eprint.iacr.org/2013/404.pdf
>>
>> Víctor Colombo (3):
>>    linux-headers/asm-powerpc/kvm.h: Add HASHKEYR and HASHPKEYR in headers
>>    target/ppc: Implement hashst and hashchk
>>    target/ppc: Implement hashstp and hashchkp
>>
>>   linux-headers/asm-powerpc/kvm.h            |  3 +
>>   target/ppc/cpu.h                           |  2 +
>>   target/ppc/cpu_init.c                      |  7 ++
>>   target/ppc/excp_helper.c                   | 82 ++++++++++++++++++++++
>>   target/ppc/helper.h                        |  4 ++
>>   target/ppc/insn32.decode                   | 10 +++
>>   target/ppc/translate.c                     |  5 ++
>>   target/ppc/translate/fixedpoint-impl.c.inc | 34 +++++++++
>>   8 files changed, 147 insertions(+)
>>


-- 
Víctor Cora Colombo
Instituto de Pesquisas ELDORADO
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