Commit 78fd6dcf authored Jun 06, 2017 by Marc Zyngier Committed by Christoffer Dall Jun 06, 2017

arm64: KVM: Allow unaligned accesses at EL2



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 <agraf@suse.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>

parent d68c1f7f

arch/arm64/kvm/hyp-init.S

+3 −2

Original line number	Diff line number	Diff line
		@@ -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