xen/arm: disable interrupts on return_to_hypervisor

At the moment it is possible to reach return_to_hypervisor with
interrupts enabled (it happens all the times when we are actually going
back to hypervisor mode, when we don't take the return_to_guest path).

If that happens we risk loosing the content of ELR_hyp: if we receive an
interrupt right after restoring ELR_hyp, once we come back we'll have a
different value in ELR_hyp and the original is lost.

In order to make the return_to_hypervisor path safe, we disable
interrupts before restoring any registers.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/xen/arch/arm/entry.S b/xen/arch/arm/entry.S
index 2ff32a183db2b895c3d83959409d2359c69c12d3..1d6ff325b034b1f60060c77e8218b221514fe363 100644 (file)
--- a/xen/arch/arm/entry.S
+++ b/xen/arch/arm/entry.S
@@ -108,6 +108,7 @@ ENTRY(return_to_guest)
        RESTORE_ONE_BANKED(R11_fiq); RESTORE_ONE_BANKED(R12_fiq);
        /* Fall thru */
 ENTRY(return_to_hypervisor)
+       cpsid i
        ldr lr, [sp, #UREGS_lr]
        ldr r11, [sp, #UREGS_pc]
        msr ELR_hyp, r11