[Xen-changelog] [xen-unstable] xen/arm: disable interrupts on return_to_hypervisor

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
# Date 1354789148 0
# Node ID d3c96e02e53270040a4f8ad0ea89796a5bf59cdd
# Parent  0c96325e2c8fbf279c0c30c8b630b1855c5945bb
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@xxxxxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Committed-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---


diff -r 0c96325e2c8f -r d3c96e02e532 xen/arch/arm/entry.S
--- a/xen/arch/arm/entry.S      Thu Dec 06 10:19:07 2012 +0000
+++ b/xen/arch/arm/entry.S      Thu Dec 06 10:19:08 2012 +0000
@@ -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

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