[Bug 1906536] Re: Unable to set SVE VL to 1024 bits or above since 7b6a2198

[Thomas Huth]

The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting the bug state to "Incomplete" now.

If the bug has already been fixed in the latest upstream version of QEMU,
then please close this ticket as "Fix released".

If it is not fixed yet and you think that this bug report here is still
valid, then you have two options:

1) If you already have an account on gitlab.com, please open a new ticket
for this problem in our new tracker here:

    https://gitlab.com/qemu-project/qemu/-/issues

and then close this ticket here on Launchpad (or let it expire auto-
matically after 60 days). Please mention the URL of this bug ticket on
Launchpad in the new ticket on GitLab.

2) If you don't have an account on gitlab.com and don't intend to get
one, but still would like to keep this ticket opened, then please switch
the state back to "New" or "Confirmed" within the next 60 days (other-
wise it will get closed as "Expired"). We will then eventually migrate
the ticket automatically to the new system (but you won't be the reporter
of the bug in the new system and thus you won't get notified on changes
anymore).

Thank you and sorry for the inconvenience.


** Changed in: qemu
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1906536

Title:
  Unable to set SVE VL to 1024 bits or above since 7b6a2198

Status in QEMU:
  Incomplete

Bug description:
  Prior to 7b6a2198e71794c851f39ac7a92d39692c786820, the QEMU option
  sve-max-vq could be used to set the vector length of the
  implementation. This is useful (among other reasons) for testing
  software compiled with a fixed SVE vector length. Since this commit,
  the vector length is capped at 512 bits.

  To reproduce the issue:

  $ cat rdvl.s
  .global _start
  _start:
    rdvl x0, #1
    asr x0, x0, #4
    mov x8, #93 // exit
    svc #0
  $ aarch64-linux-gnu-as -march=armv8.2-a+sve rdvl.s -o rdvl.o
  $ aarch64-linux-gnu-ld rdvl.o
  $ for vl in 1 2 4 8 16; do ../build-qemu/aarch64-linux-user/qemu-aarch64 -cpu 
max,sve-max-vq=$vl a.out; echo $?; done
  1
  2
  4
  4
  4

  For a QEMU built prior to the above revision, we get the output:
  1
  2
  4
  8
  16

  as expected. It seems that either the old behavior should be restored,
  or there should be an option to force a higher vector length?

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