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Re: [Qemu-arm] [PATCH v1 8/9] target-arm: A64: Create Instruction Syndro
Re: [Qemu-arm] [PATCH v1 8/9] target-arm: A64: Create Instruction Syndromes for Data Aborts
Thu, 18 Feb 2016 11:42:17 +0000
On 18 February 2016 at 09:56, Edgar E. Iglesias
> On Tue, Feb 16, 2016 at 07:13:32PM +0000, Peter Maydell wrote:
>> I think this patch also would be simpler if the encoded info
>> put in with the TBs was just the syndrome register, rather
>> than some other encoding.
> My first try was to only pass the bits needed for the iss
> (i.e not the full data abort syndrome). We don't have all
> the info needed at translation time to create the full
> syndrome (e.g stage2 trap? stage2 trap while stage1 PTW, etc).
> But we could maybe create as much of the data abort syndrome
> as possible at translation time and then have the exception
> handling code add the missing bits. We can then pass the
> preliminary syndrome from translation time to exception time
> in the std syndrome format. I can have a look and see what I
> can do if that makes more sense.
Yep, that was basically what I had in mind.
Am I right in thinking that at translate time we capture:
IL ISV SAS SSE SRT SF AR
and then at exception time we determine:
EC FnV EA CM S1PTW WnR DFSC
In that case I think you could reasonably have the info stored
with the TBs be "template syndrome >> 14" (since bits [13:0] are
all info determined at exception-time). The only reason for doing
this is that the encoded data is stored as sleb128 deltas between
lines so keeping the values numerically smaller should make them
take up a bit less space. (I have no idea how significant the
space saving would be.)
You should then be able to just have restore_state_to_opc()
write straight to env->exception.syndrome rather than needing
a new field in the cpu state.
- Re: [Qemu-arm] [PATCH v1 5/9] target-arm/translate-a64.c: Use extract32 in disas_ldst_reg_imm9, (continued)
- [Qemu-arm] [PATCH v1 4/9] target-arm: Add more fields to the data abort syndrome generator, Edgar E. Iglesias, 2016/02/12
- [Qemu-arm] [PATCH v1 7/9] target-arm: Add the ARMInsnSyndrome type, Edgar E. Iglesias, 2016/02/12
- [Qemu-arm] [PATCH v1 6/9] target-arm/translate-a64.c: Unify some of the ldst_reg decoding, Edgar E. Iglesias, 2016/02/12
- [Qemu-arm] [PATCH v1 9/9] target-arm: Use isyn.swstep.ex to hold the is_ldex state, Edgar E. Iglesias, 2016/02/12
- [Qemu-arm] [PATCH v1 8/9] target-arm: A64: Create Instruction Syndromes for Data Aborts, Edgar E. Iglesias, 2016/02/12