[Xen-devel] [PATCH 2/3] xen/arm: Allow secondary cpus to start in THUMB

[Julien Grall <julien.grall@xxxxxxxxxx>]

Unlike bx, eret will not update the instruction set (THUMB,ARM) according to
the return address. This will result to an unpredicable behaviour for the
processor if the address doesn't match the right instruction set.

When the kernel is compiled with THUMB2, THUMB bit needs to be set in CPSR
for the secondary cpus.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
---
 xen/arch/arm/psci.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/arch/arm/psci.c b/xen/arch/arm/psci.c
index 18feead..574c343 100644
--- a/xen/arch/arm/psci.c
+++ b/xen/arch/arm/psci.c
@@ -43,6 +43,9 @@ int do_psci_cpu_on(uint32_t vcpuid, register_t entry_point)
     ctxt->ttbr1 = 0;
     ctxt->ttbcr = 0; /* Defined Reset Value */
     ctxt->user_regs.cpsr = PSR_GUEST_INIT;
+    /* Start the VCPU in THUMB mode if it's requested by the kernel */
+    if ( entry_point & 1 )
+        ctxt->user_regs.cpsr |= PSR_THUMB;
     ctxt->flags = VGCF_online;
 
     domain_lock(d);
-- 
1.7.10.4


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