target/arm: Provide always-false kvm_arm_*_supported() stubs for usermode

If you try to build aarch64-linux-user with clang and --enable-debug then it
fails to compile:

 ld: libqemu-aarch64-linux-user.a.p/target_arm_cpu64.c.o: in function `cpu_arm_set_sve':
 ../../target/arm/cpu64.c:321:(.text+0x1254): undefined reference to `kvm_arm_sve_supported'

This is a regression introduced in commit f86d4220, which switched
the kvm-stub.c file away from being built for all arm targets to only
being built for system emulation binaries.  It doesn't affect gcc,
presumably because even at -O0 gcc folds away the always-false
kvm_enabled() condition but clang does not.

We would prefer not to build kvm-stub.c once for usermode and once
for system-emulation binaries, and we can't build it just once for
both because it includes cpu.h.  So instead provide always-false
versions of the five functions that are valid to call without KVM
support in kvm_arm.h.

Fixes: f86d42205c2eba ("target/arm/meson: accelerator files are not needed in user mode")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3033
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-id: 20250714135152.1896214-1-peter.maydell@linaro.org
1 file changed