From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: [PATCH 2/3] arm64: KVM: Allow unaligned accesses at EL2 Date: Tue, 6 Jun 2017 19:08:34 +0100 Message-ID: <20170606180835.14421-3-marc.zyngier@arm.com> References: <20170606180835.14421-1-marc.zyngier@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Catalin Marinas , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org To: Christoffer Dall Return-path: In-Reply-To: <20170606180835.14421-1-marc.zyngier@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org 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 --- 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 4072d408a4b4..3f9615582377 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 -- 2.11.0