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 <agraf@suse.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index 4e460d9..4bbff90 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -104,9 +104,10 @@
/*
* 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