• Arnd Bergmann's avatar
    ARM: kvm: fix building with gcc-8 · 67870eb1
    Arnd Bergmann authored
    In banked-sr.c, we use a top-level '__asm__(".arch_extension virt")'
    statement to allow compilation of a multi-CPU kernel for ARMv6
    and older ARMv7-A that don't normally support access to the banked
    registers.
    
    This is considered to be a programming error by the gcc developers
    and will no longer work in gcc-8, where we now get a build error:
    
    /tmp/cc4Qy7GR.s:34: Error: Banked registers are not available with this architecture. -- `mrs r3,SP_usr'
    /tmp/cc4Qy7GR.s:41: Error: Banked registers are not available with this architecture. -- `mrs r3,ELR_hyp'
    /tmp/cc4Qy7GR.s:55: Error: Banked registers are not available with this architecture. -- `mrs r3,SP_svc'
    /tmp/cc4Qy7GR.s:62: Error: Banked registers are not available with this architecture. -- `mrs r3,LR_svc'
    /tmp/cc4Qy7GR.s:69: Error: Banked registers are not available with this architecture. -- `mrs r3,SPSR_svc'
    /tmp/cc4Qy7GR.s:76: Error: Banked registers are not available with this architecture. -- `mrs r3,SP_abt'
    
    Passign the '-march-armv7ve' flag to gcc works, and is ok here, because
    we know the functions won't ever be called on pre-ARMv7VE machines.
    Unfortunately, older compiler versions (4.8 and earlier) do not understand
    that flag, so we still need to keep the asm around.
    
    Backporting to stable kernels (4.6+) is needed to allow those to be built
    with future compilers as well.
    
    Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84129
    Fixes: 33280b4c ("ARM: KVM: Add banked registers save/restore")
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
    Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
    67870eb1
banked-sr.c 3.57 KB