Mirror the behavour of /proc/sys/abi/sve_default_vector_length
under the real linux kernel. We have no way of passing along
a real default across exec like the kernel can, but this is a
decent way of adjusting the startup vector length of a process.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/482
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20210723203344.968563-4-richard.henderson@linaro.org
[PMM: tweaked docs formatting, document -1 special-case,
added fixup patch from RTH mentioning QEMU's maximum veclen.]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
b3d52804c5