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    Subject[PATCH 4.9 20/65] ARM: kvm: fix building with gcc-8
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    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Arnd Bergmann <arnd@arndb.de>

    commit 67870eb1204223598ea6d8a4467b482e9f5875b5 upstream.

    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: 33280b4cd1dc ("ARM: KVM: Add banked registers save/restore")
    Cc: stable@vger.kernel.org
    Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/arm/kvm/hyp/Makefile | 5 +++++
    arch/arm/kvm/hyp/banked-sr.c | 4 ++++
    2 files changed, 9 insertions(+)

    --- a/arch/arm/kvm/hyp/Makefile
    +++ b/arch/arm/kvm/hyp/Makefile
    @@ -6,6 +6,8 @@ ccflags-y += -fno-stack-protector -DDISA

    KVM=../../../../virt/kvm

    +CFLAGS_ARMV7VE :=$(call cc-option, -march=armv7ve)
    +
    obj-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hyp/vgic-v2-sr.o
    obj-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hyp/vgic-v3-sr.o
    obj-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hyp/timer-sr.o
    @@ -14,7 +16,10 @@ obj-$(CONFIG_KVM_ARM_HOST) += tlb.o
    obj-$(CONFIG_KVM_ARM_HOST) += cp15-sr.o
    obj-$(CONFIG_KVM_ARM_HOST) += vfp.o
    obj-$(CONFIG_KVM_ARM_HOST) += banked-sr.o
    +CFLAGS_banked-sr.o += $(CFLAGS_ARMV7VE)
    +
    obj-$(CONFIG_KVM_ARM_HOST) += entry.o
    obj-$(CONFIG_KVM_ARM_HOST) += hyp-entry.o
    obj-$(CONFIG_KVM_ARM_HOST) += switch.o
    +CFLAGS_switch.o += $(CFLAGS_ARMV7VE)
    obj-$(CONFIG_KVM_ARM_HOST) += s2-setup.o
    --- a/arch/arm/kvm/hyp/banked-sr.c
    +++ b/arch/arm/kvm/hyp/banked-sr.c
    @@ -20,6 +20,10 @@

    #include <asm/kvm_hyp.h>

    +/*
    + * gcc before 4.9 doesn't understand -march=armv7ve, so we have to
    + * trick the assembler.
    + */
    __asm__(".arch_extension virt");

    void __hyp_text __banked_save_state(struct kvm_cpu_context *ctxt)

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