4.9-stable review patch. If anyone has any objections, please let me know.
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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)