From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: [PULL v2 5/6] arm64: KVM: Allow unaligned accesses at EL2 Date: Wed, 7 Jun 2017 19:11:51 +0200 Message-ID: <20170607171152.21874-6-cdall@linaro.org> References: <20170607171152.21874-1-cdall@linaro.org> Return-path: In-Reply-To: <20170607171152.21874-1-cdall@linaro.org> Sender: kvm-owner@vger.kernel.org To: Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= Cc: Marc Zyngier , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org, Christoffer Dall List-Id: kvmarm@lists.cs.columbia.edu From: Marc Zyngier 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. Cc: stable@vger.kernel.org Reported-by: Alexander Graf Signed-off-by: Marc Zyngier Signed-off-by: Christoffer Dall --- arch/arm64/kvm/hyp-init.S | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S index 4072d40..3f96155 100644 --- a/arch/arm64/kvm/hyp-init.S +++ b/arch/arm64/kvm/hyp-init.S @@ -108,9 +108,10 @@ __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 -- 2.9.0