[PATCH 16/18] xen/arm: Isolate the SError between the context switch of 2 vCPUs

[Wei Chen <Wei.Chen@arm.com>]

If there is a pending SError while we are doing context switch, if the
SError handle option is "FORWARD", We have to guranatee this serror to
be caught by current vCPU, otherwise it will be caught by next vCPU and
be forwarded to this wrong vCPU.

We don't want to export serror_op accessing to other source files and
use serror_op every place, so we add a helper to synchronize SError for
context switching. The synchronize_serror has been used in this helper,
so the "#if 0" can be removed.

Signed-off-by: Wei Chen <Wei.Chen@arm.com>
---
 xen/arch/arm/domain.c           |  2 ++
 xen/arch/arm/traps.c            | 14 ++++++++++++--
 xen/include/asm-arm/processor.h |  2 ++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 69c2854..a547fcd 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -312,6 +312,8 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
 
     local_irq_disable();
 
+    prevent_forward_serror_to_next_vcpu();
+
     set_current(next);
 
     prev = __context_switch(prev, next);
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index ee7865b..b8c8389 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2899,7 +2899,6 @@ asmlinkage void do_trap_hypervisor(struct cpu_user_regs *regs)
     }
 }
 
-#if 0
 static void synchronize_serror(void)
 {
     /* Synchronize against in-flight ld/st. */
@@ -2908,7 +2907,18 @@ static void synchronize_serror(void)
     /* A single instruction exception window */
     isb();
 }
-#endif
+
+/*
+ * If the SErrors option is "FORWARD", we have to prevent forwarding
+ * serror to wrong vCPU. So before context switch, we have to use the
+ * synchronize_serror to guarantee that the pending serror would be
+ * caught by current vCPU.
+ */
+void prevent_forward_serror_to_next_vcpu(void)
+{
+    if ( serrors_op == SERRORS_FORWARD )
+        synchronize_serror();
+}
 
 asmlinkage void do_trap_hyp_serror(struct cpu_user_regs *regs)
 {
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index afad78c..3b43234 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -711,6 +711,8 @@ void do_trap_hyp_serror(struct cpu_user_regs *regs);
 
 void do_trap_guest_serror(struct cpu_user_regs *regs);
 
+void prevent_forward_serror_to_next_vcpu(void);
+
 /* Functions for pending virtual abort checking window. */
 void abort_guest_exit_start(void);
 void abort_guest_exit_end(void);
-- 
2.7.4


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