Re: [PATCH v5 20/22] tests/tcg/aarch64: add test-sve-ioctl guest-debug test

[Alex Bennée]

Richard Henderson <address@hidden> writes:

> On 1/14/20 5:09 AM, Alex Bennée wrote:
>> This test exercises the gdbstub while runing the sve-iotcl test. I
>> haven't plubmed it into make system as we need a way of verifying if
>> gdb has the right support for SVE.
>> 
>> Signed-off-by: Alex Bennée <address@hidden>
>> 
>> ---
>> v4
>>   - interrogate ZCR_EL1 directly as no longer have vg
>
> Note that ZCR_EL1 does not give you the correct answer if the hypervisor has
> set ZCR_EL2 to something lower.

Sure - although this is only a user space test so we are not expecting
shenanigans.


> Also, ZCR_EL1 it itself not correct if the
> hardware does not support all vector sizes.
>
> See some of Andrew Jones' qemu command-line work.  Try -cpu max,sve512=on and
> then use the ioctl to set vq to 3 (sve384).  The result will be an effective 
> vq
> of 2 (sve256).
>
> We *really* need vg, as computed from sve_zcr_len_for_el().

How come TARGET_PR_SVE_GET_VL is happy to compute directly from ZCR
then?

I'll put the vg back in but it seemed a little pointless given the
gdbstub ignores it.

>
>
> r~


-- 
Alex Bennée