From: Marc Zyngier Date: Tue, 6 Jun 2017 18:08:34 +0000 (+0100) Subject: arm64: KVM: Allow unaligned accesses at EL2 X-Git-Tag: v4.11.5~98 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d06ca326dd0f93074deee4845c7334d7d4df1cbd;p=thirdparty%2Fkernel%2Fstable.git arm64: KVM: Allow unaligned accesses at EL2 commit 78fd6dcf11468a5a131b8365580d0c613bcc02cb upstream. We currently have the SCTLR_EL2.A bit set, trapping unaligned accesses at EL2, but we're not really prepared to deal with it. So far, this has been unnoticed, until GCC 7 started emitting those (in particular 64bit writes on a 32bit boundary). Since the rest of the kernel is pretty happy about that, let's follow its example and set SCTLR_EL2.A to zero. Modern CPUs don't really care. Reported-by: Alexander Graf Signed-off-by: Marc Zyngier Signed-off-by: Christoffer Dall Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S index 4e460d9735603..4bbff904169d7 100644 --- a/arch/arm64/kvm/hyp-init.S +++ b/arch/arm64/kvm/hyp-init.S @@ -104,9 +104,10 @@ __do_hyp_init: /* * Preserve all the RES1 bits while setting the default flags, - * as well as the EE bit on BE. + * as well as the EE bit on BE. Drop the A flag since the compiler + * is allowed to generate unaligned accesses. */ - ldr x4, =(SCTLR_EL2_RES1 | SCTLR_ELx_FLAGS) + ldr x4, =(SCTLR_EL2_RES1 | (SCTLR_ELx_FLAGS & ~SCTLR_ELx_A)) CPU_BE( orr x4, x4, #SCTLR_ELx_EE) msr sctlr_el2, x4 isb