[Xen-devel] [for-4.7] xen/arm: Force broadcast of TLB and instruction cache maintenance instructions

[Julien Grall <julien.grall@xxxxxxx>]

UP guest usually uses TLB instruction to flush only on the local CPU. The
TLB flush won't be broadcasted across all the CPUs within the same
innershareable domain.

When the vCPU is migrated between different CPUs, it may be rescheduled
to a previous CPU where the TLB has not been flushed. The TLB may
contain stale entries which will result to translate incorrectly a VA to
IPA or even cause TLB conflicts.

To avoid a such situation, always set HCR_EL2.FB which will force the
broadcast of TLB and instruction cache maintenance instructions.
Cheers,

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---

This is a bug fix for Xen 4.7 and should be backported up to Xen 4.4
(first official release for ARM). Without this patch, UP guest will
crash if it gets migrated on a physical CPU with stale TLBs for this
guest.
---
 xen/arch/arm/traps.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 5e865cf..9926a57 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -124,7 +124,8 @@ void init_traps(void)
 
     /* Setup hypervisor traps */
     WRITE_SYSREG(HCR_PTW|HCR_BSU_INNER|HCR_AMO|HCR_IMO|HCR_FMO|HCR_VM|
-                 HCR_TWE|HCR_TWI|HCR_TSC|HCR_TAC|HCR_SWIO|HCR_TIDCP, HCR_EL2);
+                 HCR_TWE|HCR_TWI|HCR_TSC|HCR_TAC|HCR_SWIO|HCR_TIDCP|HCR_FB,
+                 HCR_EL2);
     isb();
 }
 
-- 
1.9.1


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