[PATCH 0/3] target/arm: Set FPSCR.LTPSIZE for user-mode

[Peter Maydell]

This patchset fixes https://gitlab.com/qemu-project/qemu/-/issues/613
which is a bug where we weren't setting FPSCR.LTPSIZE correctly
out of reset for the user-mode emulator. The effect is that
when using an M-profile CPU with the low-overhead-branch or MVE
extensions (ie the Cortex-M55) with the linux-user QEMU the 'LE'
instruction would take a UserFault and MVE instructions would
be incorrectly predicated.

This is the result of some over-exuberant ifdeffery in the
arm_cpu_reset() function. Patch 1 fixes that so that most of
the M-profile-specific reset handling is not ifdeffed, and
when we're in user mode we specifically set the FPU state up
cleanly. Patches 2 and 3 are just follow-on tidyup.

Christophe, if you are in a position to test this series with:
 M55 (has Security, MVE and LOB)
 M33 (has Security extension but not MVE/LOB)
 M7 or M4 (no Security, but does have FPU)
that would be ideal. I don't really have much in the way of
test cases for usermode to hand, so it's possible that I
forgot something in the init of the FPU state that might break
one of those combinations. (It does fix the test case attached
to the bug report.)

thanks
-- PMM

Peter Maydell (3):
  target/arm: Don't skip M-profile reset entirely in user mode
  target/arm: Always clear exclusive monitor on reset
  target/arm: Consolidate ifdef blocks in reset

 target/arm/cpu.c | 39 ++++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 11 deletions(-)

-- 
2.20.1