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.)
I ran the GCC testsuite with these configurations, and found no regression compared to qemu-6.0, thanks.
In the M55 case, this also enabled many more tests, which is great!
Christophe
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